[cfe-dev] clang and clang-sa do not detect uninitialized variable

[Ali Shuja Siddiqui (alissidd) via cfe-dev]

Hello,
With the following code
//-------------------------
#include <stdio.h>
extern int t;
void use_b (int *b){
    printf("%p\n",b);
}

void func(){
    int b;
    use_b(&b);
    if (b)
        b+=33;
}
//---------------------------

Running clang -Wuninitialized or running clang –analyze, I don’t see any warning for uninitialized variables. However, if I change the code to:
//----------------------
#include <stdio.h>
extern int t;
void use_b (int *b){
    if (t==5)
        return;
    printf("%p\n",b);
}

void func(){
    int b;
    use_b(&b);
    if (b)
        b+=33;
}
//--------------------
I do see this warning with the static analyzer:

sa_try.c:13:9: warning: Branch condition evaluates to a garbage value [core.uninitialized.Branch]
    if (b)
        ^
1 warning generated.

My question is why am I not getting any warning for the first case? Is it being considered that printf is updating the value of b in some way?

Thanks,
Ali
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20210429/05175245/attachment.html>