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Re: [Tinycc-devel] bug?

From: Philippe Ribet
Subject: Re: [Tinycc-devel] bug?
Date: Tue, 19 Aug 2008 22:11:31 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040413 Debian/1.6-5

John Regehr wrote:

Sorry, I mean it prints "-255".

I'm using tcc-0.9.24 on Ubnutu Linux.

John Regehr

John Regehr wrote:

For the program below, tcc emits a program that prints "255" whereas most compilers would say that the program should print "1".

Of course wrapping the signed scalar p_99 has undefined behavior, so what I am asking is: is tcc intentionally exploiting the undefinedness of the program, or is this a bug?


John Regehr

#include <stdio.h>

int g_254;

void func_97 (signed char p_99);
void func_97 (signed char p_99)
  for (; p_99; p_99 -= 1)
    g_254 = p_99;

main (void)
  func_97 (-1);
  printf ("%d\n", g_254);
  return 0;

-255 seems strange! Runing it myself, I would say -256. Strange tcc result!


            Philippe Ribet

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