Fix ABI demangling for the GCC 5.x case.

[Jo-Con-El]

When glog is compiled with gcc-5.2 in cxx11 ABI mode, it barfs about unmangled symbols. This patches it getting inspiration from binutils and demangle.cc itself, although it may be totally wrong or maybe have to use ParseAbiTag in more places. I haven't read the spec for the symbols, though.

Symbols are demangled now as

google::LogDestination::addresses_[cxx11]

This patch makes the demangle unit test pass correctly (as there's no more symbols starting with _Z), so closes #40.

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[Jo-Con-El]

Hey, yo!

[googlebot]

CLAs look good, thanks!

[Jo-Con-El]

This probably fixes #14 as well.

[ukai]

no unittest?

[vielmetti]

I applied #50 on an aarch64 system with GCC 5.4.0, and all tests related to demangling passed.

[Jo-Con-El]

Sorry, @ukai. No unittests for now. I made this patch a looong time ago and I'm not affected by this bug anymore. Moreover, I don't have bandwidth at this time to revisit this. :-(

[vielmetti]

@Jo-Con-El @ukai - where would unit tests go, if they were to exist? I am on a system where this patch matters, and it would be very useful to have it accepted.

[shinh]

I think you'll want to add symbols to https://github.com/google/glog/blob/master/src/demangle_unittest.txt

[janisz]

I tried to add a test but it fails

diff --git a/src/demangle_unittest.cc b/src/demangle_unittest.cc
index be48341..c51371a 100644
--- a/src/demangle_unittest.cc
+++ b/src/demangle_unittest.cc
@@ -111,6 +111,8 @@ TEST(Demangle, Clones) {
   EXPECT_STREQ("Foo()", tmp);
   EXPECT_TRUE(Demangle("_ZL3Foov.isra.2.constprop.18", tmp, sizeof(tmp)));
   EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_Z3fooB5cxx11", tmp, sizeof(tmp)));
+  EXPECT_STREQ("foo[abi:cxx11]", tmp);
   // Invalid (truncated), should not demangle.
   EXPECT_FALSE(Demangle("_ZL3Foov.clo", tmp, sizeof(tmp)));
   // Invalid (.clone. not followed by number), should not demangle.

although it's working in GCC

#include <stdio.h>
#include <stdlib.h>
#include <cxxabi.h>

int main() {
        const char *mangled_name = "_Z3fooB5cxx11";
        char *demangled_name;
        int status = -1;
        demangled_name = abi::__cxa_demangle(mangled_name, NULL, NULL, &status);
        printf("Demangled: %s\n", demangled_name);
        free(demangled_name);
        return 0;
}