[llvm-dev] LLD: patch to fix libCOFF calling exit() on success in a library function

[Rui Ueyama via llvm-dev]

I think I prefer adding CanExitEarly flag to COFF lld just like ELF lld. We
call `exit` at the end of link() because exiting without calling
destructors of globallly-allocated objects makes the linker noticeably
faster, so I don't want to replace it with return.

On Thu, Aug 31, 2017 at 3:16 PM, Andrew Kelley <superjoe30 at gmail.com> wrote:

> Correct, I am using libCOFF, libELF, and libMACHO all as a library.
> Ideally all cases would return and report an error and clean up memory,
> etc, instead of calling exit. However this is sufficient for my needs for
> now. It is ok for LLD to crash if I supply an invalid command line
> argument, I won't do that.
>
>
> On Thu, Aug 31, 2017 at 5:47 PM, Rui Ueyama <ruiu at google.com> wrote:
>
>> COFF lld uses exit() unlike ELF lld due to lack of user needs, but are
>> you trying to use it as a library? If so, I believe you need to fix other
>> places where exit() is called on success or for a trivial error (such as
>> invalid command line argument) as well.
>>
>> On Thu, Aug 31, 2017 at 10:45 AM, Andrew Kelley via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> I believe that LLD is not supposed to call exit on success when you
>>> call lld::coff::link.
>>>
>>> From downstream fork of LLD: https://github.com/zig-la
>>> ng/zig/commit/41da9fdb69065082f57c604b12eb02ca166cb18d
>>>
>>>
>>> diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
>>> index 854c3e69098..8b17f039870 100644
>>> --- a/lld/COFF/Driver.cpp
>>> +++ b/lld/COFF/Driver.cpp
>>> @@ -1030,7 +1030,7 @@ void LinkerDriver::link(ArrayRef<const char *>
>>> ArgsArr) {
>>>    if (!Args.hasArgNoClaim(OPT_INPUT)) {
>>>      fixupExports();
>>>      createImportLibrary(/*AsLib=*/true);
>>> -    exit(0);
>>> +    return;
>>>    }
>>>
>>>    // Handle /delayload
>>> @@ -1122,7 +1122,7 @@ void LinkerDriver::link(ArrayRef<const char *>
>>> ArgsArr) {
>>>    // This is useful because MSVC link.exe can generate complete PDBs.
>>>    if (Args.hasArg(OPT_msvclto)) {
>>>      invokeMSVC(Args);
>>> -    exit(0);
>>> +    return;
>>>    }
>>>
>>>    // Do LTO by compiling bitcode input files to a set of native COFF
>>> files then
>>> @@ -1173,8 +1173,7 @@ void LinkerDriver::link(ArrayRef<const char *>
>>> ArgsArr) {
>>>    // Write the result.
>>>    writeResult(&Symtab);
>>>
>>> -  // Call exit to avoid calling destructors.
>>> -  exit(0);
>>> +  return;
>>>  }
>>>
>>>  } // namespace coff
>>>
>>>
>>> _______________________________________________
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>>>
>>>
>>
>
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