static dtors are invoked unconditionally with -fno-use-cxa-atexit

[llvmbot]

Bugzilla Link	9593
Resolution	FIXED
Resolved on	Apr 06, 2012 21:42
Version	2.9
OS	Windows XP
Blocks	#8762 llvm/llvm-bugzilla-archive#10152
Attachments	foo.s generated by clang -fno-use-cxa-atexit, foo.s generated by cygwin's g++
Reporter	LLVM Bugzilla Contributor
CC	@asl,@rjmccall

Extended Description

// testcase
extern "C" void ctor();
extern "C" void dtor();

class FOO {
public:
FOO() {ctor();}
~FOO() {dtor();}
};

FOO* get() {
static FOO instance;
return &instance;
}

$ clang++ -cc1 -fno-use-cxa-atexit -O3 -Wall foo.cc -S -emit-llvm -o foo.ll

(snip)

define %class.FOO* @​_Z3getv() nounwind {
(check and set guard variable for get()::instance)
}

(snip)

@​llvm.global_dtors = appending global [1 x %0] [%0 { i32 65535, void ()* @​_GLOBAL__D_a }]

(snip)

define internal void @​_GLOBAL__D_a() nounwind {
entry:
tail call void @​dtor() nounwind
ret void
}

////////

Cygming is affected by this issue.
FYI, with g++-4.4 on cygming, atexit(tcf_xxx) is used instead of cxa_atexit.

[llvmbot]

Fixed in r154191.