[cfe-dev] -O4 with #include <iostream>

[Toralf Niebuhr]

I recently asked why something doesn't compile. With the latest trunk it compiles fine under some conditions.

//  ---- Out.h
class Out {
public:
  void out();
};

//  ---- Out.cpp
#include "Out.h"
#include <iostream>

void Out::out() {
  std::cout << "Hello World" << std::endl;
}

// ---- main.cpp
#include "Out.h"

int main() {
  Out o;
	o.out();
	return 0;
}

compiling this with 
clang++ -O4 -o main main.cpp Out.cpp 
gives the following error

Alloca array size must be i32
  %o = alloca %class.Out, void (%class.Out*)* @_ZN3Out3outEv, align 2 ; <%class.Out*> [#uses=1]
Instruction does not dominate all uses!
  %o = alloca %class.Out, void (%class.Out*)* @_ZN3Out3outEv, align 2 ; <%class.Out*> [#uses=1]
  call void @_ZN3Out3outEv(%class.Out* %o)
Broken module found, compilation aborted!
Stack dump:
0.	Running pass 'Function Pass Manager' on module 'ld-temp.o'.
1.	Running pass 'Module Verifier' on function '@main'


The interesting thing is the following

if I modify main.cpp to

// ---- main.cpp
#include "Out.h"
#include <iostream>

int main() {
  Out o;
	o.out();
	return 0;
}

It compiles fine and the binary runes fine too.

This makes me think that there was to much optimization done during compile time when compiling Out.cpp

Any ideas?


Toralf