Request init/fini array on FreeBSD 12 and later

[emaste]

Summary

It seems a bad idea to change the default in the middle of a release branch due to possible changes in global ctor / dtor ordering between .ctors and .init_array. With FreeBSD 11.0's release imminent lets change the default now for FreeBSD 12 (the current development stream) and later.

FreeBSD rtld has supported .init_array / .fini_array for many years. As of Jan 1 2017 all supported FreeBSD releases and branches will have support.

[dim]

LGTM.

[brooks]

Adding Alex as he made some related changes to CHERI Clang recently https://github.com/CTSRD-CHERI/clang/commit/3a648766deabb4ff7f95862213c3c99e7223363c.

[dim]

Brooks, I can commit this if you prefer. Maybe it can go into 6.0.2 still...

[brooks]

I do think we should make this change, but don't have a strong opinion on the timing. If we do it for 12 and not 13 then we should probably try to get it into a 6.0.2.

[arichardson]

I recently made this change for the CHERI clang fork and as far as I can tell everything works fine.

[bsdjhb]

Ping. I'd like this to go in and get merged into FreeBSD's clang so we can test this for a few months before 12.0 branches.

lib/Driver/ToolChains.cpp

 }
 
 void Generic_ELF::addClangTargetOptions(const ArgList &DriverArgs,
                                         ArgStringList &CC1Args) const {
   const Generic_GCC::GCCVersion &V = GCCInstallation.getVersion();
   bool UseInitArrayDefault =
       getTriple().getArch() == llvm::Triple::aarch64 ||
       getTriple().getArch() == llvm::Triple::aarch64_be ||
+      (getTriple().getOS() == llvm::Triple::FreeBSD &&
+       getTriple().getOSMajorVersion() >= 12) ||
       (getTriple().getOS() == llvm::Triple::Linux &&
        (!V.isOlderThan(4, 7, 0) || getTriple().isAndroid())) ||
       getTriple().getOS() == llvm::Triple::NaCl ||
       (getTriple().getVendor() == llvm::Triple::MipsTechnologies &&
        !getTriple().hasEnvironment());
 
   if (DriverArgs.hasFlag(options::OPT_fuse_init_array,
                          options::OPT_fno_use_init_array, UseInitArrayDefault))

test/Driver/constructors.c

 // RUN:     -target arm64-none-linux-gnu \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:     --gcc-toolchain="" \
 // RUN:   | FileCheck --check-prefix=CHECK-INIT-ARRAY %s
 //
 // RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1       \
 // RUN:     -target arm64-none-none-eabi \
 // RUN:   | FileCheck --check-prefix=CHECK-INIT-ARRAY %s
+
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1       \
+// RUN:     -target i386-unknown-freebsd11 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-INIT-ARRAY %s
+
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1       \
+// RUN:     -target i386-unknown-freebsd12 \
+// RUN:   | FileCheck --check-prefix=CHECK-INIT-ARRAY %s