2015-02-11 16:18 GMT+01:00 Francesco Mazzoli :

Relatedly, if I have some function pointer known at runtime that addresses a C function that takes some arguments, I have no way to invoke it from Haskell, since all FFI imports must be declared at compile-time, and I don't know the address of the symbol I want to execute at compile time.

You can use FunPtr and wrapper imports to convert a FunPtr into a Haskell function. https://hackage.haskell.org/package/base-4.7.0.2/docs/Foreign-Ptr.html#g:2 You may be interested in my dynamic-linker-template package [1] to avoid having to write boilerplate wrappers. For now it only works with dynamic linking from System.Posix.DynamicLinker, but it could be easily extended to support other platforms. It automatically generates wrappers for all the functions in a record as well as the code to load symbol addresses and to convert them into Haskell functions (examples [2,3]). Sylvain [1] https://hackage.haskell.org/package/dynamic-linker-template [2] https://github.com/hsyl20/dynamic-linker-template/blob/master/Tests/Test.hs [3] https://github.com/hsyl20/ViperVM/blob/master/src/lib/ViperVM/Arch/OpenCL/Li...

There's a bunch of useful info on this thread. Does anyone feel able to distill it to our main FFI wiki page: https://wiki.haskell.org/GHC/Using_the_FFI That way, future generations will benefit. (These user-oriented wiki pages are all linked from GHC's documentation page https://wiki.haskell.org/GHC.) Thanks! Simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of adam | vogt | Sent: 11 February 2015 19:32 | To: Sylvain Henry | Cc: ghc-devs@haskell.org; haskell | Subject: Re: [Haskell-cafe] Anonymous FFI calls | | On Wed, Feb 11, 2015 at 12:26 PM, Sylvain Henry wrote: | > 2015-02-11 16:18 GMT+01:00 Francesco Mazzoli : | >> | >> | >> Relatedly, if I have some function pointer known at runtime that | >> addresses a C function that takes some arguments, I have no way to | >> invoke it from Haskell, since all FFI imports must be declared at | >> compile-time, and I don't know the address of the symbol I want to | >> execute at compile time. | > | > | > You can use FunPtr and wrapper imports to convert a FunPtr into a | Haskell | > function. | > https://hackage.haskell.org/package/base-4.7.0.2/docs/Foreign- | Ptr.html#g:2 | > | > You may be interested in my dynamic-linker-template package [1] to | avoid | > having to write boilerplate wrappers. | | Code using http://hackage.haskell.org/package/libffi looks pretty | similar, though the specification needs terms (such as argCInt) | instead of a mandatory type signature. GHC itself includes libffi so | maybe the foreign import "dynamic" calls end up doing exactly the same | thing as the hackage libffi does. | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs

Another example, similar to Manuel's work but for GHCJS JavaScriptFFI is ghcjs-ffiqq: https://github.com/ghcjs/ghcjs-ffiqq . There is some automatic marshalling of arguments and results using the ToJSRef / FromJSRef typeclasses. I'm working on integrating the improvements in these typeclasses back into ghcjs-base. The quasiquoter might be moved there too, but I'm not sure yet. The (ugly) implementation is here: https://github.com/ghcjs/ghcjs-ffiqq/blob/master/src/GHCJS/Foreign/QQ.hs Adapting to ccall imports should be straightforward, but implementing the full functionality would require a bit more stub code generation, since this code depends on GHCJS' native support for inline foreign import argument placeholders ($1, $2, $3 etc) placeholders. luite On Wed, Feb 11, 2015 at 11:40 PM, Simon Peyton Jones wrote:

This may be relevant. http://www.cse.unsw.edu.au/~chak/papers/CMCK14.html Manuel gave a talk about something like this at the Haskell Symposium.

Simon

| -----Original Message----- | From: Haskell-Cafe [mailto:haskell-cafe-bounces@haskell.org] On Behalf | Of Francesco Mazzoli | Sent: 11 February 2015 10:26 | To: haskell; ghc-devs@haskell.org | Subject: [Haskell-cafe] Anonymous FFI calls | | Hi, | | I am in a situation where it would be very useful to call C functions | without an explicit FFI import. For example, I'd like to be able to | do | | (foreign import ccall "cadd" :: CInt -> CInt -> CInt) 1 2 | | instead of declaring the foreign import explicitely at the top level. | | Is there a way to do this or to achieve similar results in some other | way? | | If not, I imagine it would be easy to implement such a facility in | GHC, given that the code implementing calling to C functions must | already be present to implement "proper" FFI imports. I think such an | addition would be useful in many cases. | | Thanks, | Francesco | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe@haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs

I would LOVE someone to improve the documentation for addTopDecls. Manuel Chakravarty and Geoff Mainland were responsible for the implementation. Simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Michael | Sloan | Sent: 11 February 2015 23:19 | To: Francesco Mazzoli | Cc: ghc-devs@haskell.org; haskell | Subject: Re: [Haskell-cafe] Anonymous FFI calls | | It seems like addTopDecls[1] will able to help here. Unfortunately, | the function is not well documented and not very discoverable because | it's only exported by Language.Haskell.TH. | | The documentation doesn't mention that it can only be used to create | new top level functions and FFI imports[2]. I think that adding FFI | imports was the main motivation for implementing it. In the past | I've wanted to generate instances via this function, but unfortunately | it's not implemented.. | | Hope that helps! | -Michael | | [1] http://hackage.haskell.org/package/template-haskell- | 2.9.0.0/docs/Language-Haskell-TH-Syntax.html#v:addTopDecls | | [2] | https://github.com/ghc/ghc/blob/1d982ba10f590828b78eba992e73315dee33f78a/ | compiler/typecheck/TcSplice.hs#L818 | | On Wed, Feb 11, 2015 at 2:26 AM, Francesco Mazzoli wrote: | > Hi, | > | > I am in a situation where it would be very useful to call C functions | > without an explicit FFI import. For example, I'd like to be able to do | > | > (foreign import ccall "cadd" :: CInt -> CInt -> CInt) 1 2 | > | > instead of declaring the foreign import explicitely at the top level. | > | > Is there a way to do this or to achieve similar results in some other | > way? | > | > If not, I imagine it would be easy to implement such a facility in GHC, | > given that the code implementing calling to C functions must already be | > present to implement "proper" FFI imports. I think such an addition | > would be useful in many cases. | > | > Thanks, | > Francesco | > _______________________________________________ | > Haskell-Cafe mailing list | > Haskell-Cafe@haskell.org | > http://www.haskell.org/mailman/listinfo/haskell-cafe | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs

| Also, I meant to say that addTopDecls is only exported by | "Language.Haskell.TH.Syntax". While this is a digression, there are a | few other handy functions that are oddly left out of | "Language.Haskell.TH": addDependentFile, addModFinalizer, and possibly | more. That does seem wrong. Do make a patch! SIMon | | -Michael | | On Wed, Feb 11, 2015 at 3:25 PM, Simon Peyton Jones | wrote: | > I would LOVE someone to improve the documentation for addTopDecls. | Manuel Chakravarty and Geoff Mainland were responsible for the | implementation. | > | > Simon | > | > | -----Original Message----- | > | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of | > | Michael Sloan | > | Sent: 11 February 2015 23:19 | > | To: Francesco Mazzoli | > | Cc: ghc-devs@haskell.org; haskell | > | Subject: Re: [Haskell-cafe] Anonymous FFI calls | > | | > | It seems like addTopDecls[1] will able to help here. | Unfortunately, | > | the function is not well documented and not very discoverable | > | because it's only exported by Language.Haskell.TH. | > | | > | The documentation doesn't mention that it can only be used to | create | > | new top level functions and FFI imports[2]. I think that adding | FFI | > | imports was the main motivation for implementing it. In the past | > | I've wanted to generate instances via this function, but | > | unfortunately it's not implemented.. | > | | > | Hope that helps! | > | -Michael | > | | > | [1] http://hackage.haskell.org/package/template-haskell- | > | 2.9.0.0/docs/Language-Haskell-TH-Syntax.html#v:addTopDecls | > | | > | [2] | > | | https://github.com/ghc/ghc/blob/1d982ba10f590828b78eba992e73315dee33 | > | f78a/ | > | compiler/typecheck/TcSplice.hs#L818 | > | | > | On Wed, Feb 11, 2015 at 2:26 AM, Francesco Mazzoli | wrote: | > | > Hi, | > | > | > | > I am in a situation where it would be very useful to call C | > | > functions without an explicit FFI import. For example, I'd like | > | > to be able to do | > | > | > | > (foreign import ccall "cadd" :: CInt -> CInt -> CInt) 1 2 | > | > | > | > instead of declaring the foreign import explicitely at the top | level. | > | > | > | > Is there a way to do this or to achieve similar results in some | > | > other way? | > | > | > | > If not, I imagine it would be easy to implement such a facility | in | > | > GHC, given that the code implementing calling to C functions | must | > | > already be present to implement "proper" FFI imports. I think | > | > such an addition would be useful in many cases. | > | > | > | > Thanks, | > | > Francesco | > | > _______________________________________________ | > | > Haskell-Cafe mailing list | > | > Haskell-Cafe@haskell.org | > | > http://www.haskell.org/mailman/listinfo/haskell-cafe | > | _______________________________________________ | > | ghc-devs mailing list | > | ghc-devs@haskell.org | > | http://www.haskell.org/mailman/listinfo/ghc-devs

| Thanks to everyone who replied! | | It seems like that through a combination of facilities like `libffi' | and `addTopDecls' I can do everything that I wanted to do. Great. But please, please, do write up what you learned on the FFI wiki page https://wiki.haskell.org/GHC/Using_the_FFI Simon | -----Original Message----- | From: Francesco Mazzoli [mailto:f@mazzo.li] | Sent: 12 February 2015 09:00 | To: Simon Peyton Jones | Cc: Michael Sloan; Manuel Chakravarty; Geoffrey Mainland | (mainland@cs.drexel.edu); ghc-devs@haskell.org; haskell | Subject: Re: [Haskell-cafe] Anonymous FFI calls | | Thanks to everyone who replied! | | It seems like that through a combination of facilities like `libffi' | and `addTopDecls' I can do everything that I wanted to do. | | I still want to take a shot at implementing anonymous FFI calls, since | IMHO I think they are a very small but useful addition to the | language. | | Francesco | | On 12 February 2015 at 09:29, Simon Peyton Jones | wrote: | > | Also, I meant to say that addTopDecls is only exported by | > | "Language.Haskell.TH.Syntax". While this is a digression, there are | a | > | few other handy functions that are oddly left out of | > | "Language.Haskell.TH": addDependentFile, addModFinalizer, and | possibly | > | more. | > | > That does seem wrong. Do make a patch! | > | > SIMon | > | > | | > | -Michael | > | | > | On Wed, Feb 11, 2015 at 3:25 PM, Simon Peyton Jones | > | wrote: | > | > I would LOVE someone to improve the documentation for addTopDecls. | > | Manuel Chakravarty and Geoff Mainland were responsible for the | > | implementation. | > | > | > | > Simon | > | > | > | > | -----Original Message----- | > | > | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf | Of | > | > | Michael Sloan | > | > | Sent: 11 February 2015 23:19 | > | > | To: Francesco Mazzoli | > | > | Cc: ghc-devs@haskell.org; haskell | > | > | Subject: Re: [Haskell-cafe] Anonymous FFI calls | > | > | | > | > | It seems like addTopDecls[1] will able to help here. | > | Unfortunately, | > | > | the function is not well documented and not very discoverable | > | > | because it's only exported by Language.Haskell.TH. | > | > | | > | > | The documentation doesn't mention that it can only be used to | > | create | > | > | new top level functions and FFI imports[2]. I think that adding | > | FFI | > | > | imports was the main motivation for implementing it. In the | past | > | > | I've wanted to generate instances via this function, but | > | > | unfortunately it's not implemented.. | > | > | | > | > | Hope that helps! | > | > | -Michael | > | > | | > | > | [1] http://hackage.haskell.org/package/template-haskell- | > | > | 2.9.0.0/docs/Language-Haskell-TH-Syntax.html#v:addTopDecls | > | > | | > | > | [2] | > | > | | > | https://github.com/ghc/ghc/blob/1d982ba10f590828b78eba992e73315dee33 | > | > | f78a/ | > | > | compiler/typecheck/TcSplice.hs#L818 | > | > | | > | > | On Wed, Feb 11, 2015 at 2:26 AM, Francesco Mazzoli | > | wrote: | > | > | > Hi, | > | > | > | > | > | > I am in a situation where it would be very useful to call C | > | > | > functions without an explicit FFI import. For example, I'd | like | > | > | > to be able to do | > | > | > | > | > | > (foreign import ccall "cadd" :: CInt -> CInt -> CInt) 1 2 | > | > | > | > | > | > instead of declaring the foreign import explicitely at the top | > | level. | > | > | > | > | > | > Is there a way to do this or to achieve similar results in | some | > | > | > other way? | > | > | > | > | > | > If not, I imagine it would be easy to implement such a | facility | > | in | > | > | > GHC, given that the code implementing calling to C functions | > | must | > | > | > already be present to implement "proper" FFI imports. I think | > | > | > such an addition would be useful in many cases. | > | > | > | > | > | > Thanks, | > | > | > Francesco | > | > | > _______________________________________________ | > | > | > Haskell-Cafe mailing list | > | > | > Haskell-Cafe@haskell.org | > | > | > http://www.haskell.org/mailman/listinfo/haskell-cafe | > | > | _______________________________________________ | > | > | ghc-devs mailing list | > | > | ghc-devs@haskell.org | > | > | http://www.haskell.org/mailman/listinfo/ghc-devs

Hi, The FFI pages on the wiki are not really in a good shape in my opinion (especially for newcomers). I have started a fresh one here: https://wiki.haskell.org/Foreign_Function_Interface_(FFI) This is just the first draft. I will improve it, probably split it in several pages and merge information from other pages, especially pages linked on https://wiki.haskell.org/FFI Sylvain 2015-02-12 10:02 GMT+01:00 Simon Peyton Jones :

| Thanks to everyone who replied! | | It seems like that through a combination of facilities like `libffi' | and `addTopDecls' I can do everything that I wanted to do.

Great. But please, please, do write up what you learned on the FFI wiki page https://wiki.haskell.org/GHC/Using_the_FFI

Simon

| -----Original Message----- | From: Francesco Mazzoli [mailto:f@mazzo.li] | Sent: 12 February 2015 09:00 | To: Simon Peyton Jones | Cc: Michael Sloan; Manuel Chakravarty; Geoffrey Mainland | (mainland@cs.drexel.edu); ghc-devs@haskell.org; haskell | Subject: Re: [Haskell-cafe] Anonymous FFI calls | | Thanks to everyone who replied! | | It seems like that through a combination of facilities like `libffi' | and `addTopDecls' I can do everything that I wanted to do. | | I still want to take a shot at implementing anonymous FFI calls, since | IMHO I think they are a very small but useful addition to the | language. | | Francesco | | On 12 February 2015 at 09:29, Simon Peyton Jones | wrote: | > | Also, I meant to say that addTopDecls is only exported by | > | "Language.Haskell.TH.Syntax". While this is a digression, there are | a | > | few other handy functions that are oddly left out of | > | "Language.Haskell.TH": addDependentFile, addModFinalizer, and | possibly | > | more. | > | > That does seem wrong. Do make a patch! | > | > SIMon | > | > | | > | -Michael | > | | > | On Wed, Feb 11, 2015 at 3:25 PM, Simon Peyton Jones | > | wrote: | > | > I would LOVE someone to improve the documentation for addTopDecls. | > | Manuel Chakravarty and Geoff Mainland were responsible for the | > | implementation. | > | > | > | > Simon | > | > | > | > | -----Original Message----- | > | > | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf | Of | > | > | Michael Sloan | > | > | Sent: 11 February 2015 23:19 | > | > | To: Francesco Mazzoli | > | > | Cc: ghc-devs@haskell.org; haskell | > | > | Subject: Re: [Haskell-cafe] Anonymous FFI calls | > | > | | > | > | It seems like addTopDecls[1] will able to help here. | > | Unfortunately, | > | > | the function is not well documented and not very discoverable | > | > | because it's only exported by Language.Haskell.TH. | > | > | | > | > | The documentation doesn't mention that it can only be used to | > | create | > | > | new top level functions and FFI imports[2]. I think that adding | > | FFI | > | > | imports was the main motivation for implementing it. In the | past | > | > | I've wanted to generate instances via this function, but | > | > | unfortunately it's not implemented.. | > | > | | > | > | Hope that helps! | > | > | -Michael | > | > | | > | > | [1] http://hackage.haskell.org/package/template-haskell- | > | > | 2.9.0.0/docs/Language-Haskell-TH-Syntax.html#v:addTopDecls | > | > | | > | > | [2] | > | > | | > | https://github.com/ghc/ghc/blob/1d982ba10f590828b78eba992e73315dee33 | > | > | f78a/ | > | > | compiler/typecheck/TcSplice.hs#L818 | > | > | | > | > | On Wed, Feb 11, 2015 at 2:26 AM, Francesco Mazzoli | > | wrote: | > | > | > Hi, | > | > | > | > | > | > I am in a situation where it would be very useful to call C | > | > | > functions without an explicit FFI import. For example, I'd | like | > | > | > to be able to do | > | > | > | > | > | > (foreign import ccall "cadd" :: CInt -> CInt -> CInt) 1 2 | > | > | > | > | > | > instead of declaring the foreign import explicitely at the top | > | level. | > | > | > | > | > | > Is there a way to do this or to achieve similar results in | some | > | > | > other way? | > | > | > | > | > | > If not, I imagine it would be easy to implement such a | facility | > | in | > | > | > GHC, given that the code implementing calling to C functions | > | must | > | > | > already be present to implement "proper" FFI imports. I think | > | > | > such an addition would be useful in many cases. | > | > | > | > | > | > Thanks, | > | > | > Francesco | > | > | > _______________________________________________ | > | > | > Haskell-Cafe mailing list | > | > | > Haskell-Cafe@haskell.org | > | > | > http://www.haskell.org/mailman/listinfo/haskell-cafe | > | > | _______________________________________________ | > | > | ghc-devs mailing list | > | > | ghc-devs@haskell.org | > | > | http://www.haskell.org/mailman/listinfo/ghc-devs _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs