Thanks. I have created the Jira bug ( https://gem5.atlassian.net/browse/GEM5-1115 ) and and submitted a fix with you as reviewer.
Thanks! From: Gabe Black <gabe.bl...@gmail.com> Date: Thursday, November 18, 2021 at 11:03 PM To: gem5 Developer List <gem5-dev@gem5.org> Cc: Arun F Rodrigues <afro...@sandia.gov> Subject: [EXTERNAL] Re: [gem5-dev] Gem5 on MacOS/clang --as-needed flag detection Hi Arun, thanks for letting us know about this. Would you mind creating a bug on Jira? https://gem5.atlassian.net/jira/software/c/projects/GEM5/issues I'll have to look at this more closely, but I think this is a bug in the CheckLinkFlag check, where it should not set SHLINKFLAGS even if set_for_shared is enabled if ret is False. I don't think we want to disable set_for_shared, even though in this case it has the effect of also disabling that "if", which compensates for the fact that it's not checking ret. Like I said I'll look at the history of this code to see if I'm missing something, but I think working "ret" into the check for SHLINKFLAGS is probably what the fix should be. Could you try that? And if that works for you, would you mind uploading a fix? https://www.gem5.org/contributing Please add me as a reviewer if you do. Gabe On Thu, Nov 18, 2021 at 3:53 PM Rodrigues, Arun F via gem5-dev <gem5-dev@gem5.org<mailto:gem5-dev@gem5.org>> wrote: Hello, I’m running into some issues building libgem5 on MacOS using clang. The build compiles correctly, but fails during linking because the LLVM linker doesn’t understand the –as-needed flag. It seems that gem5 is incorrectly passing this flag. Buildline: scons build/RISCV/libgem5_opt.dylib -j 8 --without-tcmalloc Failure: [ SHLINK] -> RISCV/libgem5_opt.dylib ld: unknown option: --as-needed clang: error: linker command failed with exit code 1 (use -v to see invocation) scons: *** [build/RISCV/libgem5_opt.dylib] Error 1 The toplevel SConstruct file, line 343 has: conf.CheckLinkFlag('-Wl,--as-needed') On MacOS with clang, this check returns ‘no’ since the clang linker doesn’t take the –as-needed flag. But, it seems that CheckLinkFlag()’s default behavior (set_for_shared=True) seems to be to append the flag, even if the config test fails. Configure.py: def CheckLinkFlag(context, flag, autoadd=True, set_for_shared=True): context.Message("Checking for linker %s support... " % flag) last_linkflags = context.env['LINKFLAGS'] context.env.Append(LINKFLAGS=[flag]) ret = context.TryLink('int main(int, char *[]) { return 0; }', '.cc') if not (ret and autoadd): context.env['LINKFLAGS'] = last_linkflags if set_for_shared: assert(autoadd) context.env.Append(SHLINKFLAGS=[flag]) context.Result(ret) return ret This results in the linking phase failing on MacOS. I was able to get it to build by changing the toplevel SConstruct to: conf.CheckLinkFlag('-Wl,--as-needed', True, False) I’m not too familiar with the –as-needed flag and why it is needed, so I’m wondering: * Does this fix seem reasonable? * Is the CheckLinkFlag() behavior correct? Should the flag be appended to SHLINKFLAGS even if the test fails? Additional info: * Clang/clang++ Apple clang version 11.0.0 (clang-1100.0.33.17) * Uname -a: Darwin s1033894 19.6.0 Darwin Kernel Version 19.6.0: Sun Jul 5 00:43:10 PDT 2020; root:xnu-6153.141.1~9/RELEASE_X86_64 x86_64 Thanks, arun Thanks, arun _______________________________________________ gem5-dev mailing list -- gem5-dev@gem5.org<mailto:gem5-dev@gem5.org> To unsubscribe send an email to gem5-dev-le...@gem5.org<mailto:gem5-dev-le...@gem5.org> %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s
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