[llvm-commits] [llvm] r154124 - /llvm/trunk/tools/lto/LTOCodeGenerator.cpp

[Chris Lattner]

On Apr 6, 2012, at 12:34 AM, Duncan Sands wrote:
>> 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."
> 
> This is user error: the user should add a "used" attribute to foo.  This isn't
> anything new: lots of people make this mistake (it's come up again and again on
> the mailing list and in bugzilla).  The user should be educated here.

"What Duncan Said".  This is expected behavior - and it really is a bug in the source code.  

That said, if clang is running internalize at "clang -O4" or "clang -flto" then we should talk about whether that really is the right default.  I'm not convinced it is.  GCC has a -fwhole-program flag (or something like that) which might be appropriate.  Otherwise, the standard linker visibility stuff should be used.

-Chris