[PATCH] Defaulting to -fno-use-cxa-atexit on Windows

[Aaron Ballman]

Ping?

On Mon, Mar 11, 2013 at 9:13 PM, Aaron Ballman <aaron at aaronballman.com> wrote:
> The way MSVC handles it is by registering an atexit handler:
>
> ; 6    : C c;
>
> push OFFSET ??__Fc@@YAXXZ ; `dynamic atexit destructor for 'c''
> call _atexit
> pop ecx
> ret 0
>
> This is analogous to what clang does when passing -fno-use-cxa-atexit, which is:
>
> define internal void @__cxx_global_var_init() {
> entry:
>   %0 = call i32 @atexit(void ()* @__dtor_c) #1
>   ret void
> }
>
> ~Aaron
>
> On Mon, Mar 11, 2013 at 8:55 PM, John McCall <rjmccall at apple.com> wrote:
>> On Mar 11, 2013, at 5:30 PM, Aaron Ballman <aaron at aaronballman.com> wrote:
>>> When building for Windows, using cxa-atexit causes link errors.  We
>>> already set this flag to false for Cygywin, MinGW and hexagon targets.
>>> This patch also sets it to false for Windows targets.
>>
>> Cygwin, MinGW, and hexagon targets are Itanium ABI targets;  they're
>> just Itanium ABI targets that don't provide __cxa_atexit (although I've
>> never understood why not).  So the flag is still meaningful for them.
>> It's meaningless for MS ABI targets.
>>
>> Rather than papering over the problem, I would like someone to
>> investigate what the right code to emit is for MS ABI targets.  Specifically,
>> will the destructor get executed correctly if we just register it with LLVM
>> as a global destructor?
>>
>> John.