[PATCH] D59264: [Driver] Support compiler-rt crtbegin.o/crtend.o for Linux

Petr Hosek via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Wed Mar 13 00:27:37 PDT 2019

phosek marked an inline comment as done.
phosek added inline comments.

Comment at: clang/lib/Driver/ToolChains/Gnu.cpp:563
+          crtend = Args.hasArg(options::OPT_shared) || IsPIE || IsStaticPIE ?
+              "crtend_shared" : "crtend";
+          CmdArgs.push_back(ToolChain.getCompilerRTArgString(
MaskRay wrote:
> phosek wrote:
> > MaskRay wrote:
> > > I believe `crtbegin.o` `crtend.o` should just work. It is not necessary to use `crtbegin_shared.o` `crtend_shared.o`.
> > This is related to your comments on D28791, specifically that we should be using `crtbegin_shared.o` for `-shared` or `-pie` and `crtbegin.o` otherwise, is that not the case?
> Yes. I think we can rename `crtbegin_shared.o` to `crtbegin.o` and use it for every configuration: `-no-pie` `-pie` `-shared` `-static` `-static -pie`.
We've checked the glibc implementation of `__cxa_finalize`. A nonzero `__dso_handle` has to match the value passed to `__cxa_atexit` but a zero `__dso_handle` matches every function registered. So it matters that DSO fini calls use `&__dso_handle` to match their registrations for the `dlclose` case, but it also matters that the main executable fini call use zero to run all the dtors at exit time. It's not clear it really needs to be that way, but it would affect how the dtors get run which might affect some use cases. Hence, I don't think we can combine `crtbegin.o` and `crtbegin_shared.o`.

  rC Clang



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