In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being. “Exported” in this context only means “keep alive”. It does not mean exported in the Haskell source code sense. I’ve just added this comment to Var.hs. So I think it does just what you want. Simon data ExportFlag -- See Note [ExportFlag on binders] = NotExported -- ^ Not exported: may be discarded as dead code. | Exported -- ^ Exported: kept alive {- Note [ExportFlag on binders] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ An ExportFlag of "Exported" on a top-level binder says "keep this binding alive; do not drop it as dead code". This transititively keeps alive all the other top-level bindings that this binding refers to. This property is persisted all the way down the pipeline, so that the binding will be compiled all the way to object code, and its symbols will appear in the linker symbol table. However, note that this use of "exported" is quite different to the export list on a Haskell module. Setting the ExportFlag on an Id does /not/ mean that if you import the module (in Haskell source code you will see this Id. Of course, things that appear in the export list of the source Haskell module do indeed have their ExportFlag set. But many other things, such as dictionary functions, are kept alive by having their ExportFlag set, even though they are not exported in the source-code sense. We should probably use a different term for ExportFlag, like KeepAlive. From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Levent Erkok Sent: 06 December 2015 20:32 To: Eric Seidel ; omeragacan@gmail.com; ezyang@mit.edu Cc: ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Omer, Eric, Ed: Thanks for the comments. Omer: I think Eric's observation is at play here. We're talking about "dead-code," i.e., a binding that is neither exported, nor used by any binding inside the module. Those seem to be getting dropped by the time user-plugins are run. Unfortunately, this is precisely what one would do with "properties" embedded in code. They serve as documentation perhaps, but are otherwise not needed by any other binding nor it makes sense to export them. Edward: Can you provide some more info into your solution? Sounds like a chicken-egg issue to me: As a plugin author, I need the bindings to access the Ids, and looks like I need the Ids to access the binders? A simple solution would be to simply keep all top-level bindings around while the plugin are running, but that obviously can lead to unnecessary work if the code is truly dead. A compromise could be that the annotations can serve as entry points as well: I.e., if there's an annotation on a top-level binder, then it should *not* be considered dead-code at least until after all the plugins are run. That would definitely simplify life. Would that be an acceptable alternative? In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being. Thanks, -Levent. On Sun, Dec 6, 2015 at 11:08 AM, Eric Seidel mailto:eric@seidel.io> wrote: GHC should only drop un-exported bindings from the ModGuts if they're also unused, ie *dead code*. The only way I know to get around this is to use the bindings somewhere, or just export them. On Sat, Dec 5, 2015, at 23:01, Levent Erkok wrote:

Hello,

The mg_binds field of the ModGuts seem to only contain the bindings that are exported from the module being compiled.

I guess GHC must be running user-plugins after it drops the bindings that are not exported, which makes perfect sense for most use cases. However, I'm working on a plugin where the end-programmer embeds "properties" in the form of functions inside his/her code, which are not necessarily exported from the module under consideration.

Is there a way to access all top-level bindings in a module from a plugin, even if those bindings are not exported?

Thanks,

-Levent. _______________________________________________ ghc-devs mailing list ghc-devs@haskell.orgmailto:ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devshttps://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.haskell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc-devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cac4cbfe22e314080909908d2fe7c4ed8%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=1z6DcZxjIAKj0PcsLeALphRLWJ3i%2fxvyaPtq0qo6elY%3d

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If it's "dead" in this sense, it's already removed from ModGuts, no? Yes, if it’s dead it’s gone. That’s not too surprising, is it? So you need a way to keep it alive. Maybe we need a pragma for that. Or how would you like to signal it in the source code? Simon From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 12:05 To: Simon Peyton Jones Cc: Eric Seidel ; omeragacan@gmail.com; ezyang@mit.edu; ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Thanks Simon.. But I remain utterly confused. As a "plugin" author, how do I get my hands on the Id associated with a top-level binder? If it's "dead" in this sense, it's already removed from ModGuts, no? That is, by the time GHC runs my plugin, the Id has already disappeared for me to mark it "Local Exported." Is that not correct? On Dec 7, 2015, at 2:28 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being. “Exported” in this context only means “keep alive”. It does not mean exported in the Haskell source code sense. I’ve just added this comment to Var.hs. So I think it does just what you want. Simon data ExportFlag -- See Note [ExportFlag on binders] = NotExported -- ^ Not exported: may be discarded as dead code. | Exported -- ^ Exported: kept alive {- Note [ExportFlag on binders] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ An ExportFlag of "Exported" on a top-level binder says "keep this binding alive; do not drop it as dead code". This transititively keeps alive all the other top-level bindings that this binding refers to. This property is persisted all the way down the pipeline, so that the binding will be compiled all the way to object code, and its symbols will appear in the linker symbol table. However, note that this use of "exported" is quite different to the export list on a Haskell module. Setting the ExportFlag on an Id does /not/ mean that if you import the module (in Haskell source code you will see this Id. Of course, things that appear in the export list of the source Haskell module do indeed have their ExportFlag set. But many other things, such as dictionary functions, are kept alive by having their ExportFlag set, even though they are not exported in the source-code sense. We should probably use a different term for ExportFlag, like KeepAlive. From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Levent Erkok Sent: 06 December 2015 20:32 To: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu Cc: ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Omer, Eric, Ed: Thanks for the comments. Omer: I think Eric's observation is at play here. We're talking about "dead-code," i.e., a binding that is neither exported, nor used by any binding inside the module. Those seem to be getting dropped by the time user-plugins are run. Unfortunately, this is precisely what one would do with "properties" embedded in code. They serve as documentation perhaps, but are otherwise not needed by any other binding nor it makes sense to export them. Edward: Can you provide some more info into your solution? Sounds like a chicken-egg issue to me: As a plugin author, I need the bindings to access the Ids, and looks like I need the Ids to access the binders? A simple solution would be to simply keep all top-level bindings around while the plugin are running, but that obviously can lead to unnecessary work if the code is truly dead. A compromise could be that the annotations can serve as entry points as well: I.e., if there's an annotation on a top-level binder, then it should *not* be considered dead-code at least until after all the plugins are run. That would definitely simplify life. Would that be an acceptable alternative? In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being. Thanks, -Levent. On Sun, Dec 6, 2015 at 11:08 AM, Eric Seidel mailto:eric@seidel.io> wrote: GHC should only drop un-exported bindings from the ModGuts if they're also unused, ie *dead code*. The only way I know to get around this is to use the bindings somewhere, or just export them. On Sat, Dec 5, 2015, at 23:01, Levent Erkok wrote:

Hello,

The mg_binds field of the ModGuts seem to only contain the bindings that are exported from the module being compiled.

I guess GHC must be running user-plugins after it drops the bindings that are not exported, which makes perfect sense for most use cases. However, I'm working on a plugin where the end-programmer embeds "properties" in the form of functions inside his/her code, which are not necessarily exported from the module under consideration.

Is there a way to access all top-level bindings in a module from a plugin, even if those bindings are not exported?

Thanks,

-Levent. _______________________________________________ ghc-devs mailing list ghc-devs@haskell.orgmailto:ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devshttps://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.haskell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc-devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cac4cbfe22e314080909908d2fe7c4ed8%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=1z6DcZxjIAKj0PcsLeALphRLWJ3i%2fxvyaPtq0qo6elY%3d

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Indeed. How about this: if there's an ANN on a binder (any ANN), then GHC should keep it alive. Really? It might be something like “don’t give warnings for this binding” or “don’t inline me” or something. To say *any* annotation seems a bit brutal doesn’t it? Mind you I don’t have a better idea. One thought: your plugin could add a pass right at the start, which marks everything you want as keep-alive. S From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 12:42 To: Simon Peyton Jones Cc: Eric Seidel ; omeragacan@gmail.com; ezyang@mit.edu; ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Indeed. How about this: if there's an ANN on a binder (any ANN), then GHC should keep it alive. Is that something one of the core-developers can implement? Happy to open a ticket if that helps. On Dec 7, 2015, at 4:14 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: If it's "dead" in this sense, it's already removed from ModGuts, no? Yes, if it’s dead it’s gone. That’s not too surprising, is it? So you need a way to keep it alive. Maybe we need a pragma for that. Or how would you like to signal it in the source code? Simon From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 12:05 To: Simon Peyton Jones mailto:simonpj@microsoft.com> Cc: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu; ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Thanks Simon.. But I remain utterly confused. As a "plugin" author, how do I get my hands on the Id associated with a top-level binder? If it's "dead" in this sense, it's already removed from ModGuts, no? That is, by the time GHC runs my plugin, the Id has already disappeared for me to mark it "Local Exported." Is that not correct? On Dec 7, 2015, at 2:28 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being. “Exported” in this context only means “keep alive”. It does not mean exported in the Haskell source code sense. I’ve just added this comment to Var.hs. So I think it does just what you want. Simon data ExportFlag -- See Note [ExportFlag on binders] = NotExported -- ^ Not exported: may be discarded as dead code. | Exported -- ^ Exported: kept alive {- Note [ExportFlag on binders] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ An ExportFlag of "Exported" on a top-level binder says "keep this binding alive; do not drop it as dead code". This transititively keeps alive all the other top-level bindings that this binding refers to. This property is persisted all the way down the pipeline, so that the binding will be compiled all the way to object code, and its symbols will appear in the linker symbol table. However, note that this use of "exported" is quite different to the export list on a Haskell module. Setting the ExportFlag on an Id does /not/ mean that if you import the module (in Haskell source code you will see this Id. Of course, things that appear in the export list of the source Haskell module do indeed have their ExportFlag set. But many other things, such as dictionary functions, are kept alive by having their ExportFlag set, even though they are not exported in the source-code sense. We should probably use a different term for ExportFlag, like KeepAlive. From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Levent Erkok Sent: 06 December 2015 20:32 To: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu Cc: ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Omer, Eric, Ed: Thanks for the comments. Omer: I think Eric's observation is at play here. We're talking about "dead-code," i.e., a binding that is neither exported, nor used by any binding inside the module. Those seem to be getting dropped by the time user-plugins are run. Unfortunately, this is precisely what one would do with "properties" embedded in code. They serve as documentation perhaps, but are otherwise not needed by any other binding nor it makes sense to export them. Edward: Can you provide some more info into your solution? Sounds like a chicken-egg issue to me: As a plugin author, I need the bindings to access the Ids, and looks like I need the Ids to access the binders? A simple solution would be to simply keep all top-level bindings around while the plugin are running, but that obviously can lead to unnecessary work if the code is truly dead. A compromise could be that the annotations can serve as entry points as well: I.e., if there's an annotation on a top-level binder, then it should *not* be considered dead-code at least until after all the plugins are run. That would definitely simplify life. Would that be an acceptable alternative? In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being. Thanks, -Levent. On Sun, Dec 6, 2015 at 11:08 AM, Eric Seidel mailto:eric@seidel.io> wrote: GHC should only drop un-exported bindings from the ModGuts if they're also unused, ie *dead code*. The only way I know to get around this is to use the bindings somewhere, or just export them. On Sat, Dec 5, 2015, at 23:01, Levent Erkok wrote:

Hello,

The mg_binds field of the ModGuts seem to only contain the bindings that are exported from the module being compiled.

I guess GHC must be running user-plugins after it drops the bindings that are not exported, which makes perfect sense for most use cases. However, I'm working on a plugin where the end-programmer embeds "properties" in the form of functions inside his/her code, which are not necessarily exported from the module under consideration.

Is there a way to access all top-level bindings in a module from a plugin, even if those bindings are not exported?

Thanks,

-Levent. _______________________________________________ ghc-devs mailing list ghc-devs@haskell.orgmailto:ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devshttps://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.haskell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc-devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cac4cbfe22e314080909908d2fe7c4ed8%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=1z6DcZxjIAKj0PcsLeALphRLWJ3i%2fxvyaPtq0qo6elY%3d

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Plugins get to edit the entire core-to-core pipeline! There is no magic. At least I don’t think so file:///Z:/tmp/users_guide/compiler-plugins.html S From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 13:11 To: Simon Peyton Jones Cc: Eric Seidel ; omeragacan@gmail.com; ezyang@mit.edu; ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings That's a good point; keeping all annotated bindings alive seems to be an overkill.. Regarding implementing "pass at the start." I'm not sure if plugin authors have any freedom as to decide when their plugin actually runs. It seems GHC magically determines the order and runs them. Can you point me to some code/docs that tells me how to go "first" in that sense? (Or at least before the pass that drops dead code.) On Dec 7, 2015, at 4:45 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: Indeed. How about this: if there's an ANN on a binder (any ANN), then GHC should keep it alive. Really? It might be something like “don’t give warnings for this binding” or “don’t inline me” or something. To say *any* annotation seems a bit brutal doesn’t it? Mind you I don’t have a better idea. One thought: your plugin could add a pass right at the start, which marks everything you want as keep-alive. S From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 12:42 To: Simon Peyton Jones mailto:simonpj@microsoft.com> Cc: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu; ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Indeed. How about this: if there's an ANN on a binder (any ANN), then GHC should keep it alive. Is that something one of the core-developers can implement? Happy to open a ticket if that helps. On Dec 7, 2015, at 4:14 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: If it's "dead" in this sense, it's already removed from ModGuts, no? Yes, if it’s dead it’s gone. That’s not too surprising, is it? So you need a way to keep it alive. Maybe we need a pragma for that. Or how would you like to signal it in the source code? Simon From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 12:05 To: Simon Peyton Jones mailto:simonpj@microsoft.com> Cc: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu; ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Thanks Simon.. But I remain utterly confused. As a "plugin" author, how do I get my hands on the Id associated with a top-level binder? If it's "dead" in this sense, it's already removed from ModGuts, no? That is, by the time GHC runs my plugin, the Id has already disappeared for me to mark it "Local Exported." Is that not correct? On Dec 7, 2015, at 2:28 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being. “Exported” in this context only means “keep alive”. It does not mean exported in the Haskell source code sense. I’ve just added this comment to Var.hs. So I think it does just what you want. Simon data ExportFlag -- See Note [ExportFlag on binders] = NotExported -- ^ Not exported: may be discarded as dead code. | Exported -- ^ Exported: kept alive {- Note [ExportFlag on binders] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ An ExportFlag of "Exported" on a top-level binder says "keep this binding alive; do not drop it as dead code". This transititively keeps alive all the other top-level bindings that this binding refers to. This property is persisted all the way down the pipeline, so that the binding will be compiled all the way to object code, and its symbols will appear in the linker symbol table. However, note that this use of "exported" is quite different to the export list on a Haskell module. Setting the ExportFlag on an Id does /not/ mean that if you import the module (in Haskell source code you will see this Id. Of course, things that appear in the export list of the source Haskell module do indeed have their ExportFlag set. But many other things, such as dictionary functions, are kept alive by having their ExportFlag set, even though they are not exported in the source-code sense. We should probably use a different term for ExportFlag, like KeepAlive. From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Levent Erkok Sent: 06 December 2015 20:32 To: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu Cc: ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings Omer, Eric, Ed: Thanks for the comments. Omer: I think Eric's observation is at play here. We're talking about "dead-code," i.e., a binding that is neither exported, nor used by any binding inside the module. Those seem to be getting dropped by the time user-plugins are run. Unfortunately, this is precisely what one would do with "properties" embedded in code. They serve as documentation perhaps, but are otherwise not needed by any other binding nor it makes sense to export them. Edward: Can you provide some more info into your solution? Sounds like a chicken-egg issue to me: As a plugin author, I need the bindings to access the Ids, and looks like I need the Ids to access the binders? A simple solution would be to simply keep all top-level bindings around while the plugin are running, but that obviously can lead to unnecessary work if the code is truly dead. A compromise could be that the annotations can serve as entry points as well: I.e., if there's an annotation on a top-level binder, then it should *not* be considered dead-code at least until after all the plugins are run. That would definitely simplify life. Would that be an acceptable alternative? In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being. Thanks, -Levent. On Sun, Dec 6, 2015 at 11:08 AM, Eric Seidel mailto:eric@seidel.io> wrote: GHC should only drop un-exported bindings from the ModGuts if they're also unused, ie *dead code*. The only way I know to get around this is to use the bindings somewhere, or just export them. On Sat, Dec 5, 2015, at 23:01, Levent Erkok wrote:

Hello,

The mg_binds field of the ModGuts seem to only contain the bindings that are exported from the module being compiled.

I guess GHC must be running user-plugins after it drops the bindings that are not exported, which makes perfect sense for most use cases. However, I'm working on a plugin where the end-programmer embeds "properties" in the form of functions inside his/her code, which are not necessarily exported from the module under consideration.

Is there a way to access all top-level bindings in a module from a plugin, even if those bindings are not exported?

Thanks,

-Levent. _______________________________________________ ghc-devs mailing list ghc-devs@haskell.orgmailto:ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devshttps://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.haskell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc-devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cac4cbfe22e314080909908d2fe7c4ed8%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=1z6DcZxjIAKj0PcsLeALphRLWJ3i%2fxvyaPtq0qo6elY%3d

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The problem, as I recall, is that GHC does an initial bit of dead-code elimination in the desugarer, before the plugins have a chance to run. (I believe this is part of simpleOptPgm, but may be mistaken) I'm not sure why this is done in the desugarer, it seems to be out of place there. On Mon, Dec 7, 2015, at 05:14, Simon Peyton Jones wrote:

Plugins get to edit the entire core-to-core pipeline! There is no magic. At least I don’t think so

file:///Z:/tmp/users_guide/compiler-plugins.html

S

From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 13:11 To: Simon Peyton Jones Cc: Eric Seidel ; omeragacan@gmail.com; ezyang@mit.edu; ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings

That's a good point; keeping all annotated bindings alive seems to be an overkill..

Regarding implementing "pass at the start." I'm not sure if plugin authors have any freedom as to decide when their plugin actually runs. It seems GHC magically determines the order and runs them. Can you point me to some code/docs that tells me how to go "first" in that sense? (Or at least before the pass that drops dead code.)

On Dec 7, 2015, at 4:45 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: Indeed. How about this: if there's an ANN on a binder (any ANN), then GHC should keep it alive.

Really? It might be something like “don’t give warnings for this binding” or “don’t inline me” or something. To say *any* annotation seems a bit brutal doesn’t it? Mind you I don’t have a better idea.

One thought: your plugin could add a pass right at the start, which marks everything you want as keep-alive.

S

From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 12:42 To: Simon Peyton Jones mailto:simonpj@microsoft.com> Cc: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu; ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings

Indeed. How about this: if there's an ANN on a binder (any ANN), then GHC should keep it alive.

Is that something one of the core-developers can implement? Happy to open a ticket if that helps.

On Dec 7, 2015, at 4:14 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: If it's "dead" in this sense, it's already removed from ModGuts, no?

Yes, if it’s dead it’s gone. That’s not too surprising, is it?

So you need a way to keep it alive. Maybe we need a pragma for that. Or how would you like to signal it in the source code?

Simon

From: Levent Erkok [mailto:erkokl@gmail.com] Sent: 07 December 2015 12:05 To: Simon Peyton Jones mailto:simonpj@microsoft.com> Cc: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu; ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings

Thanks Simon.. But I remain utterly confused. As a "plugin" author, how do I get my hands on the Id associated with a top-level binder? If it's "dead" in this sense, it's already removed from ModGuts, no?

That is, by the time GHC runs my plugin, the Id has already disappeared for me to mark it "Local Exported." Is that not correct?

On Dec 7, 2015, at 2:28 AM, Simon Peyton Jones mailto:simonpj@microsoft.com> wrote: In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being.

“Exported” in this context only means “keep alive”. It does not mean exported in the Haskell source code sense. I’ve just added this comment to Var.hs.

So I think it does just what you want.

Simon

data ExportFlag -- See Note [ExportFlag on binders] = NotExported -- ^ Not exported: may be discarded as dead code. | Exported -- ^ Exported: kept alive

{- Note [ExportFlag on binders] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ An ExportFlag of "Exported" on a top-level binder says "keep this binding alive; do not drop it as dead code". This transititively keeps alive all the other top-level bindings that this binding refers to. This property is persisted all the way down the pipeline, so that the binding will be compiled all the way to object code, and its symbols will appear in the linker symbol table.

However, note that this use of "exported" is quite different to the export list on a Haskell module. Setting the ExportFlag on an Id does /not/ mean that if you import the module (in Haskell source code you will see this Id. Of course, things that appear in the export list of the source Haskell module do indeed have their ExportFlag set. But many other things, such as dictionary functions, are kept alive by having their ExportFlag set, even though they are not exported in the source-code sense.

We should probably use a different term for ExportFlag, like KeepAlive.

From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Levent Erkok Sent: 06 December 2015 20:32 To: Eric Seidel mailto:eric@seidel.io>; omeragacan@gmail.commailto:omeragacan@gmail.com; ezyang@mit.edumailto:ezyang@mit.edu Cc: ghc-devs@haskell.orgmailto:ghc-devs@haskell.org Subject: Re: Plugins: Accessing unexported bindings

Omer, Eric, Ed: Thanks for the comments.

Omer: I think Eric's observation is at play here. We're talking about "dead-code," i.e., a binding that is neither exported, nor used by any binding inside the module. Those seem to be getting dropped by the time user-plugins are run. Unfortunately, this is precisely what one would do with "properties" embedded in code. They serve as documentation perhaps, but are otherwise not needed by any other binding nor it makes sense to export them.

Edward: Can you provide some more info into your solution? Sounds like a chicken-egg issue to me: As a plugin author, I need the bindings to access the Ids, and looks like I need the Ids to access the binders?

A simple solution would be to simply keep all top-level bindings around while the plugin are running, but that obviously can lead to unnecessary work if the code is truly dead. A compromise could be that the annotations can serve as entry points as well: I.e., if there's an annotation on a top-level binder, then it should *not* be considered dead-code at least until after all the plugins are run. That would definitely simplify life. Would that be an acceptable alternative?

In the mean time, I'm still looking for a solution that doesn't involve exporting such identifiers from modules. As Eric pointed out, that seems to be the only current work-around for the time being.

Thanks,

-Levent.

On Sun, Dec 6, 2015 at 11:08 AM, Eric Seidel mailto:eric@seidel.io> wrote: GHC should only drop un-exported bindings from the ModGuts if they're also unused, ie *dead code*.

The only way I know to get around this is to use the bindings somewhere, or just export them.

On Sat, Dec 5, 2015, at 23:01, Levent Erkok wrote:

...

Hello,

The mg_binds field of the ModGuts seem to only contain the bindings that are exported from the module being compiled.

I guess GHC must be running user-plugins after it drops the bindings that are not exported, which makes perfect sense for most use cases. However, I'm working on a plugin where the end-programmer embeds "properties" in the form of functions inside his/her code, which are not necessarily exported from the module under consideration.

Is there a way to access all top-level bindings in a module from a plugin, even if those bindings are not exported?

Thanks,

-Levent. _______________________________________________ ghc-devs mailing list ghc-devs@haskell.orgmailto:ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devshttps://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.haskell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc-devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cac4cbfe22e314080909908d2fe7c4ed8%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=1z6DcZxjIAKj0PcsLeALphRLWJ3i%2fxvyaPtq0qo6elY%3d

---

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Thanks for the explanation, Simon. I think Eric is spot on. Looking at some of the "ghc -v3" output, it appears GHC always runs the following passes before any plugins are run: *** Simplify: *** CorePrep: *** ByteCodeGen: *** Desugar: Just judging by the name, it could either be the first "Simplify" or the "Desugar" that gets rid of the dead-code at this point, I'm not sure which. It would help if this stage didn't remove dead-bindings. If doing so automatically is not the best option, requiring a user given pragma like 'KeepAlive' wouldn't be too onerous either. -Levent. On Mon, Dec 7, 2015 at 8:22 AM, Simon Peyton Jones wrote:

It would not be hard to stop the desugarer dropping dead bindings, if that was helpful.

S

| -----Original Message----- | From: Eric Seidel [mailto:eric@seidel.io] | Sent: 07 December 2015 15:44 | To: Simon Peyton Jones | Cc: Levent Erkok ; omeragacan@gmail.com; | ezyang@mit.edu; ghc-devs@haskell.org | Subject: Re: Plugins: Accessing unexported bindings | | The problem, as I recall, is that GHC does an initial bit of dead-code | elimination in the desugarer, before the plugins have a chance to run. | (I believe this is part of simpleOptPgm, but may be mistaken) | | I'm not sure why this is done in the desugarer, it seems to be out of | place there. | | On Mon, Dec 7, 2015, at 05:14, Simon Peyton Jones wrote: | > Plugins get to edit the entire core-to-core pipeline! There is no | magic. | > At least I don’t think so | > | > file:///Z:/tmp/users_guide/compiler-plugins.html | > | > S | > | > From: Levent Erkok [mailto:erkokl@gmail.com] | > Sent: 07 December 2015 13:11 | > To: Simon Peyton Jones | > Cc: Eric Seidel ; omeragacan@gmail.com; | > ezyang@mit.edu; ghc-devs@haskell.org | > Subject: Re: Plugins: Accessing unexported bindings | > | > That's a good point; keeping all annotated bindings alive seems to | be | > an overkill.. | > | > Regarding implementing "pass at the start." I'm not sure if plugin | > authors have any freedom as to decide when their plugin actually | runs. | > It seems GHC magically determines the order and runs them. Can you | > point me to some code/docs that tells me how to go "first" in that | > sense? (Or at least before the pass that drops dead code.) | > | > On Dec 7, 2015, at 4:45 AM, Simon Peyton Jones | > mailto:simonpj@microsoft.com> wrote: | > Indeed. How about this: if there's an ANN on a binder (any ANN), | then | > GHC should keep it alive. | > | > Really? It might be something like “don’t give warnings for this | > binding” or “don’t inline me” or something. To say *any* | annotation | > seems a bit brutal doesn’t it? Mind you I don’t have a better | idea. | > | > One thought: your plugin could add a pass right at the start, which | > marks everything you want as keep-alive. | > | > S | > | > From: Levent Erkok [mailto:erkokl@gmail.com] | > Sent: 07 December 2015 12:42 | > To: Simon Peyton Jones | > mailto:simonpj@microsoft.com> | > Cc: Eric Seidel mailto:eric@seidel.io>; | > omeragacan@gmail.commailto:omeragacan@gmail.com; | > ezyang@mit.edumailto:ezyang@mit.edu; | > ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > Subject: Re: Plugins: Accessing unexported bindings | > | > Indeed. How about this: if there's an ANN on a binder (any ANN), | then | > GHC should keep it alive. | > | > Is that something one of the core-developers can implement? Happy to | > open a ticket if that helps. | > | > On Dec 7, 2015, at 4:14 AM, Simon Peyton Jones | > mailto:simonpj@microsoft.com> wrote: | > If it's "dead" in this sense, it's already removed from ModGuts, no? | > | > Yes, if it’s dead it’s gone. That’s not too surprising, is it? | > | > So you need a way to keep it alive. Maybe we need a pragma for that. | Or | > how would you like to signal it in the source code? | > | > Simon | > | > From: Levent Erkok [mailto:erkokl@gmail.com] | > Sent: 07 December 2015 12:05 | > To: Simon Peyton Jones | > mailto:simonpj@microsoft.com> | > Cc: Eric Seidel mailto:eric@seidel.io>; | > omeragacan@gmail.commailto:omeragacan@gmail.com; | > ezyang@mit.edumailto:ezyang@mit.edu; | > ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > Subject: Re: Plugins: Accessing unexported bindings | > | > Thanks Simon.. But I remain utterly confused. As a "plugin" author, | > how do I get my hands on the Id associated with a top-level binder? | If | > it's "dead" in this sense, it's already removed from ModGuts, no? | > | > That is, by the time GHC runs my plugin, the Id has already | > disappeared for me to mark it "Local Exported." Is that not correct? | > | > On Dec 7, 2015, at 2:28 AM, Simon Peyton Jones | > mailto:simonpj@microsoft.com> wrote: | > In the mean time, I'm still looking for a solution that doesn't | > involve exporting such identifiers from modules. As Eric pointed | out, | > that seems to be the only current work-around for the time being. | > | > “Exported” in this context only means “keep alive”. It does not mean | > exported in the Haskell source code sense. I’ve just added this | > comment to Var.hs. | > | > So I think it does just what you want. | > | > Simon | > | > data ExportFlag -- See Note [ExportFlag on binders] | > = NotExported -- ^ Not exported: may be discarded as dead code. | > | Exported -- ^ Exported: kept alive | > | > {- Note [ExportFlag on binders] | > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | > An ExportFlag of "Exported" on a top-level binder says "keep this | > binding alive; do not drop it as dead code". This transititively | > keeps alive all the other top-level bindings that this binding | refers | > to. This property is persisted all the way down the pipeline, so | that | > the binding will be compiled all the way to object code, and its | > symbols will appear in the linker symbol table. | > | > However, note that this use of "exported" is quite different to the | > export list on a Haskell module. Setting the ExportFlag on an Id | does | > /not/ mean that if you import the module (in Haskell source code you | > will see this Id. Of course, things that appear in the export list | of | > the source Haskell module do indeed have their ExportFlag set. | > But many other things, such as dictionary functions, are kept alive | by | > having their ExportFlag set, even though they are not exported in | the | > source-code sense. | > | > We should probably use a different term for ExportFlag, like | > KeepAlive. | > | > From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of | > Levent Erkok | > Sent: 06 December 2015 20:32 | > To: Eric Seidel mailto:eric@seidel.io>; | > omeragacan@gmail.commailto:omeragacan@gmail.com; | > ezyang@mit.edumailto:ezyang@mit.edu | > Cc: ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > Subject: Re: Plugins: Accessing unexported bindings | > | > Omer, Eric, Ed: Thanks for the comments. | > | > Omer: I think Eric's observation is at play here. We're talking | about | > "dead-code," i.e., a binding that is neither exported, nor used by | any | > binding inside the module. Those seem to be getting dropped by the | > time user-plugins are run. Unfortunately, this is precisely what one | > would do with "properties" embedded in code. They serve as | > documentation perhaps, but are otherwise not needed by any other | > binding nor it makes sense to export them. | > | > Edward: Can you provide some more info into your solution? Sounds | like | > a chicken-egg issue to me: As a plugin author, I need the bindings | to | > access the Ids, and looks like I need the Ids to access the binders? | > | > A simple solution would be to simply keep all top-level bindings | > around while the plugin are running, but that obviously can lead to | > unnecessary work if the code is truly dead. A compromise could be | that | > the annotations can serve as entry points as well: I.e., if there's | an | > annotation on a top-level binder, then it should *not* be considered | > dead-code at least until after all the plugins are run. That would | > definitely simplify life. Would that be an acceptable alternative? | > | > In the mean time, I'm still looking for a solution that doesn't | > involve exporting such identifiers from modules. As Eric pointed | out, | > that seems to be the only current work-around for the time being. | > | > Thanks, | > | > -Levent. | > | > On Sun, Dec 6, 2015 at 11:08 AM, Eric Seidel | > mailto:eric@seidel.io> wrote: | > GHC should only drop un-exported bindings from the ModGuts if | they're | > also unused, ie *dead code*. | > | > The only way I know to get around this is to use the bindings | > somewhere, or just export them. | > | > On Sat, Dec 5, 2015, at 23:01, Levent Erkok wrote: | > > Hello, | > > | > > The mg_binds field of the ModGuts seem to only contain the | bindings | > > that are exported from the module being compiled. | > > | > > I guess GHC must be running user-plugins after it drops the | bindings | > > that are not exported, which makes perfect sense for most use | cases. | > > However, I'm working on a plugin where the end-programmer embeds | > > "properties" in the form of functions inside his/her code, which | are | > > not necessarily exported from the module under consideration. | > > | > > Is there a way to access all top-level bindings in a module from a | > > plugin, even if those bindings are not exported? | > > | > > Thanks, | > > | > > -Levent. | > > _______________________________________________ | > > ghc-devs mailing list | > > ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > > | https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail | > > .haskell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc- | devs&data=01%7c01% | > > | 7csimonpj%40064d.mgd.microsoft.com%7cf6e3a9d4ad9f4e53a3ab08d2ff1d493 | > > | 4%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=Bv7lpsB%2fD88nSMuB7NY | > > | fBqR90%2bBq%2fwpJJ0JU9%2b6E4RI%3d<https://na01.safelinks.protection. | > > outlook.com/?url=http%3a%2f%2fmail.haskell.org%2fcgi- | bin%2fmailman%2 | > > flistinfo%2fghc- | devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com | > > | %7cac4cbfe22e314080909908d2fe7c4ed8%7c72f988bf86f141af91ab2d7cd011db | > > 47%7c1&sdata=1z6DcZxjIAKj0PcsLeALphRLWJ3i%2fxvyaPtq0qo6elY%3d> | > _______________________________________________ | > ghc-devs mailing list | > ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > | https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.h | > askell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc- | devs&data=01%7c01%7csi | > | monpj%40064d.mgd.microsoft.com%7cf6e3a9d4ad9f4e53a3ab08d2ff1d4934%7c72 | > | f988bf86f141af91ab2d7cd011db47%7c1&sdata=Bv7lpsB%2fD88nSMuB7NYfBqR90%2 | > | bBq%2fwpJJ0JU9%2b6E4RI%3d<https://na01.safelinks.protection.outlook.co | > m/?url=http%3a%2f%2fmail.haskell.org%2fcgi- | bin%2fmailman%2flistinfo%2f | > ghc- | devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cac4cbfe22e3 | > | 14080909908d2fe7c4ed8%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=1z6 | > DcZxjIAKj0PcsLeALphRLWJ3i%2fxvyaPtq0qo6elY%3d> | >

http://ghc.haskell.org/trac/ghc/ticket/11179#ticket Thanks! -Levent. On Tue, Dec 8, 2015 at 4:33 AM, Simon Peyton Jones wrote:

I think it’s probably the desugarer, and the plugin can’t do anything before desugaring!

By all means open a ticket. I can advise if anyone wants to take it up.

Simon

*From:* Levent Erkok [mailto:erkokl@gmail.com] *Sent:* 08 December 2015 03:32

*To:* Simon Peyton Jones *Cc:* Eric Seidel ; omeragacan@gmail.com; ezyang@mit.edu; ghc-devs@haskell.org *Subject:* Re: Plugins: Accessing unexported bindings

Thanks for the explanation, Simon. I think Eric is spot on. Looking at some of the "ghc -v3" output, it appears GHC always runs the following passes before any plugins are run:

*** Simplify:

*** CorePrep:

*** ByteCodeGen:

*** Desugar:

Just judging by the name, it could either be the first "Simplify" or the "Desugar" that gets rid of the dead-code at this point, I'm not sure which.

It would help if this stage didn't remove dead-bindings. If doing so automatically is not the best option, requiring a user given pragma like 'KeepAlive' wouldn't be too onerous either.

-Levent.

On Mon, Dec 7, 2015 at 8:22 AM, Simon Peyton Jones wrote:

It would not be hard to stop the desugarer dropping dead bindings, if that was helpful.

S

| -----Original Message----- | From: Eric Seidel [mailto:eric@seidel.io] | Sent: 07 December 2015 15:44 | To: Simon Peyton Jones

| Cc: Levent Erkok ; omeragacan@gmail.com; | ezyang@mit.edu; ghc-devs@haskell.org | Subject: Re: Plugins: Accessing unexported bindings | | The problem, as I recall, is that GHC does an initial bit of dead-code | elimination in the desugarer, before the plugins have a chance to run. | (I believe this is part of simpleOptPgm, but may be mistaken) | | I'm not sure why this is done in the desugarer, it seems to be out of | place there. | | On Mon, Dec 7, 2015, at 05:14, Simon Peyton Jones wrote: | > Plugins get to edit the entire core-to-core pipeline! There is no | magic. | > At least I don’t think so | > | > file:///Z:/tmp/users_guide/compiler-plugins.html | > | > S | > | > From: Levent Erkok [mailto:erkokl@gmail.com] | > Sent: 07 December 2015 13:11 | > To: Simon Peyton Jones | > Cc: Eric Seidel ; omeragacan@gmail.com; | > ezyang@mit.edu; ghc-devs@haskell.org | > Subject: Re: Plugins: Accessing unexported bindings | > | > That's a good point; keeping all annotated bindings alive seems to | be | > an overkill.. | > | > Regarding implementing "pass at the start." I'm not sure if plugin | > authors have any freedom as to decide when their plugin actually | runs. | > It seems GHC magically determines the order and runs them. Can you | > point me to some code/docs that tells me how to go "first" in that | > sense? (Or at least before the pass that drops dead code.) | > | > On Dec 7, 2015, at 4:45 AM, Simon Peyton Jones | > mailto:simonpj@microsoft.com> wrote: | > Indeed. How about this: if there's an ANN on a binder (any ANN), | then | > GHC should keep it alive. | > | > Really? It might be something like “don’t give warnings for this | > binding” or “don’t inline me” or something. To say *any* | annotation | > seems a bit brutal doesn’t it? Mind you I don’t have a better | idea. | > | > One thought: your plugin could add a pass right at the start, which | > marks everything you want as keep-alive. | > | > S | > | > From: Levent Erkok [mailto:erkokl@gmail.com] | > Sent: 07 December 2015 12:42 | > To: Simon Peyton Jones | > mailto:simonpj@microsoft.com> | > Cc: Eric Seidel mailto:eric@seidel.io>; | > omeragacan@gmail.commailto:omeragacan@gmail.com; | > ezyang@mit.edumailto:ezyang@mit.edu; | > ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > Subject: Re: Plugins: Accessing unexported bindings | > | > Indeed. How about this: if there's an ANN on a binder (any ANN), | then | > GHC should keep it alive. | > | > Is that something one of the core-developers can implement? Happy to | > open a ticket if that helps. | > | > On Dec 7, 2015, at 4:14 AM, Simon Peyton Jones | > mailto:simonpj@microsoft.com> wrote: | > If it's "dead" in this sense, it's already removed from ModGuts, no? | > | > Yes, if it’s dead it’s gone. That’s not too surprising, is it? | > | > So you need a way to keep it alive. Maybe we need a pragma for that. | Or | > how would you like to signal it in the source code? | > | > Simon | > | > From: Levent Erkok [mailto:erkokl@gmail.com] | > Sent: 07 December 2015 12:05 | > To: Simon Peyton Jones | > mailto:simonpj@microsoft.com> | > Cc: Eric Seidel mailto:eric@seidel.io>; | > omeragacan@gmail.commailto:omeragacan@gmail.com; | > ezyang@mit.edumailto:ezyang@mit.edu; | > ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > Subject: Re: Plugins: Accessing unexported bindings | > | > Thanks Simon.. But I remain utterly confused. As a "plugin" author, | > how do I get my hands on the Id associated with a top-level binder? | If | > it's "dead" in this sense, it's already removed from ModGuts, no? | > | > That is, by the time GHC runs my plugin, the Id has already | > disappeared for me to mark it "Local Exported." Is that not correct? | > | > On Dec 7, 2015, at 2:28 AM, Simon Peyton Jones | > mailto:simonpj@microsoft.com> wrote: | > In the mean time, I'm still looking for a solution that doesn't | > involve exporting such identifiers from modules. As Eric pointed | out, | > that seems to be the only current work-around for the time being. | > | > “Exported” in this context only means “keep alive”. It does not mean | > exported in the Haskell source code sense. I’ve just added this | > comment to Var.hs. | > | > So I think it does just what you want. | > | > Simon | > | > data ExportFlag -- See Note [ExportFlag on binders] | > = NotExported -- ^ Not exported: may be discarded as dead code. | > | Exported -- ^ Exported: kept alive | > | > {- Note [ExportFlag on binders] | > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | > An ExportFlag of "Exported" on a top-level binder says "keep this | > binding alive; do not drop it as dead code". This transititively | > keeps alive all the other top-level bindings that this binding | refers | > to. This property is persisted all the way down the pipeline, so | that | > the binding will be compiled all the way to object code, and its | > symbols will appear in the linker symbol table. | > | > However, note that this use of "exported" is quite different to the | > export list on a Haskell module. Setting the ExportFlag on an Id | does | > /not/ mean that if you import the module (in Haskell source code you | > will see this Id. Of course, things that appear in the export list | of | > the source Haskell module do indeed have their ExportFlag set. | > But many other things, such as dictionary functions, are kept alive | by | > having their ExportFlag set, even though they are not exported in | the | > source-code sense. | > | > We should probably use a different term for ExportFlag, like | > KeepAlive. | > | > From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of | > Levent Erkok | > Sent: 06 December 2015 20:32 | > To: Eric Seidel mailto:eric@seidel.io>; | > omeragacan@gmail.commailto:omeragacan@gmail.com; | > ezyang@mit.edumailto:ezyang@mit.edu | > Cc: ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > Subject: Re: Plugins: Accessing unexported bindings | > | > Omer, Eric, Ed: Thanks for the comments. | > | > Omer: I think Eric's observation is at play here. We're talking | about | > "dead-code," i.e., a binding that is neither exported, nor used by | any | > binding inside the module. Those seem to be getting dropped by the | > time user-plugins are run. Unfortunately, this is precisely what one | > would do with "properties" embedded in code. They serve as | > documentation perhaps, but are otherwise not needed by any other | > binding nor it makes sense to export them. | > | > Edward: Can you provide some more info into your solution? Sounds | like | > a chicken-egg issue to me: As a plugin author, I need the bindings | to | > access the Ids, and looks like I need the Ids to access the binders? | > | > A simple solution would be to simply keep all top-level bindings | > around while the plugin are running, but that obviously can lead to | > unnecessary work if the code is truly dead. A compromise could be | that | > the annotations can serve as entry points as well: I.e., if there's | an | > annotation on a top-level binder, then it should *not* be considered | > dead-code at least until after all the plugins are run. That would | > definitely simplify life. Would that be an acceptable alternative? | > | > In the mean time, I'm still looking for a solution that doesn't | > involve exporting such identifiers from modules. As Eric pointed | out, | > that seems to be the only current work-around for the time being. | > | > Thanks, | > | > -Levent. | > | > On Sun, Dec 6, 2015 at 11:08 AM, Eric Seidel | > mailto:eric@seidel.io> wrote: | > GHC should only drop un-exported bindings from the ModGuts if | they're | > also unused, ie *dead code*. | > | > The only way I know to get around this is to use the bindings | > somewhere, or just export them. | > | > On Sat, Dec 5, 2015, at 23:01, Levent Erkok wrote: | > > Hello, | > > | > > The mg_binds field of the ModGuts seem to only contain the | bindings | > > that are exported from the module being compiled. | > > | > > I guess GHC must be running user-plugins after it drops the | bindings | > > that are not exported, which makes perfect sense for most use | cases. | > > However, I'm working on a plugin where the end-programmer embeds | > > "properties" in the form of functions inside his/her code, which | are | > > not necessarily exported from the module under consideration. | > > | > > Is there a way to access all top-level bindings in a module from a | > > plugin, even if those bindings are not exported? | > > | > > Thanks, | > > | > > -Levent. | > > _______________________________________________ | > > ghc-devs mailing list | > > ghc-devs@haskell.orgmailto:ghc-devs@haskell.org | > >

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