The internalize pass can be dangerous for LTO.
Consider the following program:
$ cat main.c
void foo(void) { }
int main(int argc, char *argv[]) {
foo();
return 0;
}
$ cat bundle.c
extern void foo(void);
void bar(void) {
foo();
}
$ clang -o main main.c
$ clang -o bundle.so bundle.c -bundle -bundle_loader ./main
$ nm -m bundle.so
0000000000000f40 (__TEXT,__text) external _bar
(undefined) external _foo (from executable)
(undefined) external dyld_stub_binder (from libSystem)
$ clang -o main main.c -O4
$ clang -o bundle.so bundle.c -bundle -bundle_loader ./main
Undefined symbols for architecture x86_64:
"_foo", referenced from:
_bar in bundle-elQN6d.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
The linker was told that the 'foo' in 'main' was 'internal' and had no uses, so
it was dead stripped.
Another situation is something like:
define void @foo() {
ret void
}
define void @bar() {
call asm volatile "call _foo" ...
ret void
}
The only use of 'foo' is inside of an inline ASM call. Since we don't look
inside those for uses of functions, we don't specify this as a "use."
Get around this by not invoking the 'internalize' pass by default. This is an
admitted hack for LTO correctness.
<rdar://problem/11185386>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154124 91177308-0d34-0410-b5e6-96231b3b80d8
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