bug#45303: #45303 [feature/native-comp] building error on Windows

[Andy Moreton <andrewjmoreton@gmail.com>]

On Sat 19 Dec 2020, Eli Zaretskii wrote:

>> From: Andy Moreton <andrewjmoreton@gmail.com>
>> Date: Sat, 19 Dec 2020 17:15:02 +0000
>> 
>> > I must be missing something, because I don't see strsignal used on
>> > master in the MinGW build at all.  Moreover, Gnulib's strsignal.c is
>> > not even in lib/.  We call sigdescr_np instead.  So I wonder how did
>> > you see that the Gnulib replacement for strsignal is used on master in
>> > the Windows build.
>> 
>> Entirely possible that I have misunderstood something from reading
>> sources and grepping (the gnulib gyrations are hard to follow).
>> 
>> The emacs source calls strsignal, and something provides it (whether via
>> a macro replacement or a linkable symbol). The only difference I could
>> see was the configure test, as noted above.
>
> The ultimate test is this:
>
>   gdb ./emacs.exe
>   GNU gdb (GDB) 10.1
>   Copyright (C) 2020 Free Software Foundation, Inc.
>   ...
>   (gdb) rbreak strsignal
>
> On my system, I see just this:
>
>   Breakpoint 2 at 0x119b88b: file sysdep.c, line 2617.
>   const char *safe_strsignal(int);

Agreed, but emacs has to actually link before I can run it under GDB.

>> I see that src/syssignal.h has a replacement macro:
>> 
>>     #ifndef HAVE_STRSIGNAL
>>     # define strsignal(sig) safe_strsignal (sig)
>>     #endif
>> 
>> So is the problem that on the native branch the configure test succeeds
>> and sets HAVE_STRSIGNAL, resulting in trying to link the wrong symbol ?
>
> Possibly.  The question is, how come the test succeeds?  Can you look
> in libjccjit.a with "nm -A" and see if it exports strsignal?

/c/home/ajm/tmp> nm -A /mingw32/lib/libgccjit.dll.a | grep strsignal
C:/msys64/mingw32/lib/libgccjit.dll.a:d025440.o:00000000 I __imp__strsignal
C:/msys64/mingw32/lib/libgccjit.dll.a:d025440.o:00000000 T _strsignal

/c/home/ajm/tmp> nm -A /mingw64/lib/libgccjit.dll.a | grep strsignal
C:/msys64/mingw64/lib/libgccjit.dll.a:d025724.o:0000000000000000 I __imp_strsignal
C:/msys64/mingw64/lib/libgccjit.dll.a:d025724.o:0000000000000000 T strsignal

Yes, it would appear so.

    AndyM