incorrect signed/unsigned conversions for short and char

[eben]

Binary package hint: gcc-4.2

Release:

Description: Ubuntu 8.04
Release: 8.04

Version information:

gcc-4.2:
  Installed: 4.2.3-2ubuntu7
  Candidate: 4.2.3-2ubuntu7
  Version table:
 *** 4.2.3-2ubuntu7 0
        500 http://us.archive.ubuntu.com hardy/main Packages
        100 /var/lib/dpkg/status

Description:

Signed/unsigned comparisons yield unexpected results in some cases. C code that exercises this is appears below. The expected result (tested on previous versions of gcc) is that it will print the gcc version and nothing else.

#include <stdio.h>

int main() {

    long l = 0L;
    unsigned long ul = 0x80000000L;

    int i = 0;
    unsigned int ui = 0x80000000;

    short s = 0;
    unsigned short us = 0x8000;

    char c = 0;
    unsigned char uc = 0x80;

    printf("Using gcc version %s\n\n", __VERSION__);

    if (l > ul)
        printf("long 0x%08lx > unsigned long 0x%08lx evaluates to true\n", l, ul);

    if (i > ui)
        printf("int 0x%08x > unsigned int 0x%08x evaluates to true\n", i, ui);

    if (s > us)
        printf("short 0x%04x > unsigned short 0x%04x evaluates to true\n", s, us);

    if (c > uc)
        printf("char 0x%02x > unsigned char 0x%02x evaluates to true\n", c, uc);

    if (((long) 0L) > ((unsigned long) 0x80000000L))
        printf("((long) 0L) > ((unsigned long) 0x80000000L) evaluates to true\n");

    if (((int) 0) > ((unsigned char) 0x8000000))
        printf("((int) 0) > ((unsigned int) 0x8000000) evaluates to true\n");

    if (((char) 0) > ((unsigned short) 0x8000))
        printf("((short) 0) > ((unsigned short) 0x8000) evaluates to true\n");

    if (((char) 0) > ((unsigned char) 0x80))
        printf("((char) 0) > ((unsigned char) 0x80) evaluates to true\n");

    return 0;
}

$ gcc -Wall test.c -o test
$ ./test

Using gcc version 4.2.3 (Ubuntu 4.2.3-2ubuntu7)

short 0x0000 > unsigned short 0x8000 evaluates to true
char 0x00 > unsigned char 0x80 evaluates to true