SV: Windows breakage -- again

Niklas Larsson metaniklas at
Fri Jul 18 14:21:18 UTC 2014

I posted a working and tested patch last night. Please feel free to commit it, I haven't the rights to do it.


----- Ursprungligt meddelande -----
Från: "Simon Peyton Jones" <simonpj at>
Skickat: ‎2014-‎07-‎18 15:55
Till: "Niklas Larsson" <metaniklas at>; "Johan Tibell" <johan.tibell at>
Kopia: "ghc-devs at" <ghc-devs at>
Ämne: RE: Windows breakage -- again

Thank you all for pursuing this.  I gather that you know what is going on, so no further info needed from me.  Yell if it is otherwise.
Meanwhile, is the fix imminent, or should we revert Johan’s patch?
From: Niklas Larsson [mailto:metaniklas at] 
Sent: 16 July 2014 19:58
To: Johan Tibell; Simon Peyton Jones
Cc: ghc-devs at
Subject: Re: Windows breakage -- again
I get the same failure when I try to build HEAD. Turns out the error occurs on the 32-bit Windows build, and my successful build was a 64-bit build. My 64-bit build still succeeds.
Also, gcc is 4.5.2 on 32-bit, not 4.6.3 as on 64-bit.
2014-07-16 14:48 GMT+02:00 Niklas Larsson <metaniklas at>:
I have built ghc on windows after that was added with no issue.

I can take a look this evening and  see how HEAD works for me.

The standard gcc in the tarballs is 4.6.3, which is getting long in the tooth, there is an issue on trac to upgrade it. 

-- Niklas

Från: Johan Tibell
Skickat: ‎2014-‎07-‎16 09:57
Till: Simon Peyton Jones
Kopia: ghc-devs at
Ämne: Re: Windows breakage -- again
You can rollback the commit (git revert 4ee4ab01c1d97845aecb7707ad2f9a80933e7a49) and push that to the repo if you wish. I will try to re-add the primop again after I figure out what's wrong.
On Wed, Jul 16, 2014 at 9:37 AM, Johan Tibell <johan.tibell at> wrote:
I added some primops about a month ago (4ee4ab01c1d97845aecb7707ad2f9a80933e7a49) that call __sync_fetch_and_add, a gcc/llvm builtin. I'm a bit surprised to see this error. The GCC manual [1] says: 
> " Not all operations are supported by all target processors. If a particular operation cannot be implemented on the target processor, a warning will be generated and a call an external function will be generated. The external function will carry the same name as the builtin, with an additional suffix `_n' where n is the size of the data type."
I'm a bit surprised by this error for two reasons:
 * A call to that symbol should only be generated if the CPU doesn't support the atomic instructions. What CPU model does Windows report that you have?
 * gcc should define such a symbol. For me the following test program compiles:
#include <stdint.h>
uint8_t test(uint8_t* ptr, uint8_t val) {
  return __sync_fetch_and_add_1(ptr, val);
int main(void) {
  uint8_t n;
  return test(&n, 1);
Does that compile for you? Which version of GCC do we end up using on Windows?
The reported symbol (___sync_fetch_and_add_1) has three leading underscores, that looks weird. Can you compile just libraries/ghc-prim/cbits/atomic.c and see if it's indeed GCC that generates a reference to that symbol?
On Wed, Jul 16, 2014 at 12:29 AM, Simon Peyton Jones <simonpj at> wrote:
Aargh!  The Windows build has broken – again.  I can’t build GHC on my laptop any more.  

[Hela det ursprungliga meddelandet tas inte med.]
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