#10688: Incorrect program produced, different result with equivalent code -------------------------------------+------------------------------------- Reporter: Ideophage | Owner: Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by Ideophage): * priority: normal => lowest Old description:

The program enters an infinite loop (100% cpu, not stopping) because it fails to recognize the stopping condition of a takeWhile. If we make the list finite, it takes all the elements while it should stop before.

I don't know how to simplify the code since if I change it a little (e.g. by replacing the name of an object by its definition), sometimes it works well, sometimes not.

When I enter the code in ghci, it works well but not when compiled.

I don't know if I should explain what the code was for initially, tell me.

New description: The program enters an infinite loop (100% cpu, not stopping) because it fails to recognize the stopping condition of a `takeWhile`. If we make the list finite, it takes all the elements while it should stop before. I don't know how to simplify the code since if I change it a little (e.g. by replacing the name of an object by its definition), sometimes it works well, sometimes not. When I enter the code in ghci, it works well but not when compiled. I don't know if I should explain what the code was for initially, tell me. edit : Actually, I realized that this is not a bug. This is due to the lack of type signatures in my program. I thought that was a bug because sometimes the program used `Int`s, sometimes `Integer`s, and just expanding a definition can change this (see the code in attachment). I apologize for opening a ticket for that (I thought `Integer`s were used since it is the case in ghci). -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10688#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10688: Incorrect program produced, different result with equivalent code -------------------------------------+------------------------------------- Reporter: Ideophage | Owner: Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Description changed by Ideophage: Old description:

The program enters an infinite loop (100% cpu, not stopping) because it fails to recognize the stopping condition of a `takeWhile`. If we make the list finite, it takes all the elements while it should stop before.

I don't know how to simplify the code since if I change it a little (e.g. by replacing the name of an object by its definition), sometimes it works well, sometimes not.

When I enter the code in ghci, it works well but not when compiled.

I don't know if I should explain what the code was for initially, tell me.

edit : Actually, I realized that this is not a bug. This is due to the lack of type signatures in my program. I thought that was a bug because sometimes the program used `Int`s, sometimes `Integer`s, and just expanding a definition can change this (see the code in attachment). I apologize for opening a ticket for that (I thought `Integer`s were used since it is the case in ghci).

New description: edit : Actually, I realized that this is not a bug. This is due to the lack of type signatures in my program. I thought that was a bug because sometimes the program used `Int`s, sometimes `Integer`s, and just expanding a definition can change this (see the code in attachment). I apologize for opening a ticket for that (I thought `Integer`s were used since it is the case in ghci). Below my original message. The program enters an infinite loop (100% cpu, not stopping) because it fails to recognize the stopping condition of a `takeWhile`. If we make the list finite, it takes all the elements while it should stop before. I don't know how to simplify the code since if I change it a little (e.g. by replacing the name of an object by its definition), sometimes it works well, sometimes not. When I enter the code in ghci, it works well but not when compiled. I don't know if I should explain what the code was for initially, tell me. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10688#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10688: Incorrect program produced, different result with equivalent code -------------------------------------+------------------------------------- Reporter: Ideophage | Owner: Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by Ideophage): * Attachment "bug1.2.hs" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10688 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

Is it possible to upload a (presumably large) program which reproduces

#10688: Incorrect program produced, different result with equivalent code -------------------------------------+------------------------------------- Reporter: Ideophage | Owner: Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by Ideophage): Replying to [comment:1 ezyang]: the problem? Even some code snippets would help; what's the stopping condition of `takeWhile`? Can you reproduce with `-O0`? Can you try with 7.10.2 or even the latest master version of GHC? Some description of what the code does would also be useful. Thanks for your reply. I checked the box for adding an attachment and I thought my ticket was not opened. I added the code. This is reproducible with `-O0`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10688#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10688: Incorrect program produced, different result with equivalent code -------------------------------------+------------------------------------- Reporter: Ideophage | Owner: Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by Ideophage): * Attachment "bug1.2.hs" added. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10688 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10688: Incorrect program produced, different result with equivalent code -------------------------------------+------------------------------------- Reporter: Ideophage | Owner: Type: bug | Status: closed Priority: lowest | Milestone: Component: Compiler | Version: 7.10.1 Resolution: invalid | Keywords: Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by simonpj): Interesting. Now that you understand what went wrong, you could write a note explaining the trap you fell into, and share it with others. It is, after all, rather surprising when you are told "omit a type signature and you get an infinite loop". Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10688#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10688: Incorrect program produced, different result with equivalent code -------------------------------------+------------------------------------- Reporter: Ideophage | Owner: Type: bug | Status: closed Priority: lowest | Milestone: Component: Compiler | Version: 7.10.1 Resolution: invalid | Keywords: Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by rwbarton): Right, it's not a bug, but it is a confusing consequence of the monomorphism restriction together with defaulting and type inference. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10688#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler