Crash with range-based for loops, local variables, own collection class and -Wuninitialized

[llvmbot]

Bugzilla Link	9741
Resolution	FIXED
Resolved on	Apr 18, 2011 10:51
Version	unspecified
OS	MacOS X
Attachments	Clang's log of the compile
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@zygoloid

Extended Description

The following program results in a crashing clang during compilation when being compiled with -Wuninitialized (see attached log which also includes the clang version used):

#include

template
class ArrayRef {
public:
T* begin() const { return m_begin; }
T* end() const { return m_end; }

private:
	T*	m_begin;
	T*	m_end;

};

//static void doIt(std::vector ints) // (A)
static void doIt(ArrayRef ints)
{
// (B) Commenting this line makes the error disappear
unsigned int u = 0;

for (const int& i : ints) ;

// (C)
//for (auto it = ints.begin(), end = ints.end(); it != end; ++it) ;

}

int main(int, char**)
{
}

The crash does not occur, if I

• use std::vector instead of ArrayRef (line A)
• comment line B
• use a traditional for loop with iterators instead of the range-based for
  loop (line C)

[llvmbot]

assigned to @zygoloid

[llvmbot]

It seems that one of the local variables created for the range-based for loop is not being tracked during the check for uninitialized variables, even though it is included in the checks. But why only when a custom collection is used?

Also, the stack trace in the attached log seems weird.

[zygoloid]

This does not fail if the iterator type is a class type: the -Wuninitialized checks don't apply then. The failure is caused by the implicit variable declarations not being added to the surrounding declaration context.

The stack trace issue is probably a problem with your build setup; I get a sensible stack trace.

[zygoloid]

Fixed in r129700.