c++ front end failed to initialize a "__thread" local "bool" variable with value "true" in a multi-threaded environment. I also did more tests, it could initialize the variable to "false" correctly. Also it could initialize an "int" variable correctly.

The bug would also be reproduced with both driver "gcc" and "g++":

witch@desktop:/tmp$ g++ --version
g++ (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

witch@desktop:/tmp$ cat t.cpp
#include <stdio.h>
#include <pthread.h>

void g(bool x) {
	printf("%d\n", x);
}

void* f(void* arg) {
	static __thread bool i = true;
	g(i);
	return NULL;
}

int main() {
	pthread_t a, b;
	pthread_create(&a, NULL, &f, NULL);
	pthread_create(&b, NULL, &f, NULL);
	pthread_join(a, NULL);
	pthread_join(b, NULL);
	return 0;
}
witch@desktop:/tmp$ g++ t.cpp -O2 -pthread
witch@desktop:/tmp$ ./a.out 
1
1
witch@desktop:/tmp$ g++ t.cpp -O0 -pthread
witch@desktop:/tmp$ ./a.out 
0
0