Bug 15539

gcc -v output :
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Reading specs from /usr/lib/gcc-lib/i486-linux/3.3.3/specs
Configured with: ../src/configure -v
--enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-gxx-include-dir=/usr/include/c++/3.3 --enable-shared --with-system-zlib
--enable-nls --without-included-gettext --enable-__cxa_atexit
--enable-clocale=gnu --enable-debug --enable-java-gc=boehm
--enable-java-awt=xlib --enable-objc-gc i486-linux
Thread model: posix
gcc version 3.3.3 (Debian 20040429)
****************


I was writing a fonction "isnumber" to find is a string is a number. So I used
strtol, but I made a mistake, which produce the text :
****************
isnumber.c: In function `isnumber':
isnumber.c:14: error: Attempt to delete prologue/epilogue insn:
(insn/f 80 79 81 0 (nil) (set (mem:SI (plus:SI (reg/f:SI 6 ebp)
                (const_int -4 [0xfffffffc])) [0 S4 A8])
        (reg:SI 3 ebx)) -1 (nil)
    (nil))
isnumber.c:14: internal compiler error: in propagate_one_insn, at flow.c:1642
Please submit a full bug report,
****************

After some tests, I found that this is produce only with some kinds of -O
optimization..

I have extracted two examples that doesn't compile :
****************
/* gcc flag
 *  -O0 : works
 *  -O1 : works
 *  -O2 : doesn't work
 *  -O3 : doesn't work
 */
int isnumber1_bug(const char *chaine) {
  char *endptr[1];
  endptr[1] = '\0';
  strtol(chaine,endptr,10);
  return *chaine != '\0' && **endptr == '\0';
}
****************
/* gcc flag
 *  -O0 : works
 *  -O1 : doesn't work
 *  -O2 : doesn't work
 *  -O3 : doesn't work
 */
int isnumber2_bug(const char *chaine) {
  char *endptr[1];
  endptr[1] = '\0';
  strtol(chaine,(char **)NULL,10);
  return *chaine != '\0';
}
****************

of course, the right way is to write "*endptr[1] = '\0';", that was my mistake...

but what is strange is that this :
****************
/* this works ! */
int isnumber1(const char *chaine) {
  char *endptr[1];
  endptr[1] = '\0';
  strtol(chaine,endptr,10);
  return **endptr == '\0';
}
****************
..is working : just the last line changed...

How-To-Repeat:
just with "gcc -O2 -c -o isnumber.o isnumber.c", and try with other -O
optimization flags...

;-]