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RE: Missing warning about uninitialized variable.

At the end of the original message I did include the command lines of three
different compilations, using gcc 4.0.4, 4.1.3 and 4.2.3, all with the same
basic command line: gcc -O -Wall -o foo foo.c

Only the first version, gcc 4.0.4, prints the warning.


-----Original Message-----
From: Tom St Denis [] 
Sent: den 29 november 2007 19:23
To: Mikael Vidstedt
Cc: 'J.C. Pizarro';
Subject: Re: Missing warning about uninitialized variable.

Mikael Vidstedt wrote:
> Just a quick question: Did anybody actually read the subject? My question
> was not about the value of the variable, it was about recent GCC versions
> longer warn about the use of an uninitialized variable...?

You have to turn on the optimizer to see that.  As I understand it, it's 
only when the optimizer walks down the tree that it picks up the 
uninitialized bit.

-bash-3.00$ gcc -O -Wall -c warn.c
warn.c: In function `main':
warn.c:4: warning: 'g' might be used uninitialized in this function
-bash-3.00$ cat warn.c
#include <stdio.h>
int main(int argc, char **argv)
  int g;
  if (argc == 10) { g = 3; }
  printf("g == %d\n", g);
  return 0;


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