I am running debian sarge in a PowerBook G3, kernel 2.6.8.
When I try to compile this code:
$ cat pp.c
#include<stdio.h>
main(){
char c=-1;
if(c < 0){
printf("hola\n");
}
}
I get this error:
$ gcc pp.c
pp.c: In function `main':
pp.c:7: warning: comparison is always false due to limited range of data type
I have tested it with no trouble in gcc 2.95 (debian woody i386),gcc 3.2.3
(slackware i386), gcc 3.3 (MacOSX, ppc). I have noted that if the comparison is
against 1 ( if(c < 0) ... ) the error do not occurs.
This is the output using the -v -save-temps options:
$ gcc -v -save-temps pp.c
Reading specs from /usr/lib/gcc-lib/powerpc-linux/3.3.4/specs
Configured with: ../src/configure -v
--enable-languages=c,c++,java,f77,pascal,objc,ada --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 --disable-multilib powerpc-linux
Thread model: posix
gcc version 3.3.4 (Debian 1:3.3.4-3)
/usr/lib/gcc-lib/powerpc-linux/3.3.4/cc1 -E -quiet -v -D__GNUC__=3
-D__GNUC_MINOR__=3 -D__GNUC_PATCHLEVEL__=4 -D__unix__ -D__gnu_linux__
-D__linux__ -Dunix -D__unix -Dlinux -D__linux -Asystem=unix -Asystem=posix pp.c
pp.i
ignoring nonexistent directory "/usr/powerpc-linux/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/usr/lib/gcc-lib/powerpc-linux/3.3.4/include
/usr/include
End of search list.
/usr/lib/gcc-lib/powerpc-linux/3.3.4/cc1 -fpreprocessed pp.i -quiet -dumpbase
pp.c -auxbase pp -version -o pp.s
GNU C version 3.3.4 (Debian 1:3.3.4-3) (powerpc-linux)
compiled by GNU C version 3.3.4 (Debian 1:3.3.4-3).
GGC heuristics: --param ggc-min-expand=38 --param ggc-min-heapsize=15840
pp.c: In function `main':
pp.c:7: warning: comparison is always false due to limited range of data type
as -mppc -V -Qy -o pp.o pp.s
GNU assembler version 2.14.90.0.7 (powerpc-linux) using BFD version 2.14.90.0.7
20031029 Debian GNU/Linux
/usr/lib/gcc-lib/powerpc-linux/3.3.4/collect2 --eh-frame-hdr -V -Qy -m
elf32ppclinux -dynamic-linker /lib/ld.so.1
/usr/lib/gcc-lib/powerpc-linux/3.3.4/../../../crt1.o
/usr/lib/gcc-lib/powerpc-linux/3.3.4/../../../crti.o
/usr/lib/gcc-lib/powerpc-linux/3.3.4/crtbegin.o
-L/usr/lib/gcc-lib/powerpc-linux/3.3.4
-L/usr/lib/gcc-lib/powerpc-linux/3.3.4/../../.. pp.o -lgcc -lgcc_eh -lc -lgcc
-lgcc_eh /usr/lib/gcc-lib/powerpc-linux/3.3.4/crtsavres.o
/usr/lib/gcc-lib/powerpc-linux/3.3.4/crtend.o
/usr/lib/gcc-lib/powerpc-linux/3.3.4/../../../crtn.o
GNU ld version 2.14.90.0.7 20031029 Debian GNU/Linux
Supported emulations:
elf32ppclinux
elf32ppc
elf32ppcsim
elf64ppc
And this is the contets of the pp.i file:
$ cat pp.i
# 1 "pp.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "pp.c"
# 1 "/usr/include/stdio.h" 1 3 4
# 28 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/features.h" 1 3 4
# 295 "/usr/include/features.h" 3 4
# 1 "/usr/include/sys/cdefs.h" 1 3 4
# 296 "/usr/include/features.h" 2 3 4
# 318 "/usr/include/features.h" 3 4
# 1 "/usr/include/gnu/stubs.h" 1 3 4
# 319 "/usr/include/features.h" 2 3 4
# 29 "/usr/include/stdio.h" 2 3 4
# 1 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 1 3 4
# 213 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 3 4
typedef unsigned int size_t;
# 35 "/usr/include/stdio.h" 2 3 4
# 1 "/usr/include/bits/types.h" 1 3 4
# 28 "/usr/include/bits/types.h" 3 4
# 1 "/usr/include/bits/wordsize.h" 1 3 4
# 29 "/usr/include/bits/types.h" 2 3 4
# 1 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 1 3 4
# 32 "/usr/include/bits/types.h" 2 3 4
typedef unsigned char __u_char;
typedef unsigned short int __u_short;
typedef unsigned int __u_int;
typedef unsigned long int __u_long;
typedef signed char __int8_t;
typedef unsigned char __uint8_t;
typedef signed short int __int16_t;
typedef unsigned short int __uint16_t;
typedef signed int __int32_t;
typedef unsigned int __uint32_t;
__extension__ typedef signed long long int __int64_t;
__extension__ typedef unsigned long long int __uint64_t;
__extension__ typedef long long int __quad_t;
__extension__ typedef unsigned long long int __u_quad_t;
# 129 "/usr/include/bits/types.h" 3 4
# 1 "/usr/include/bits/typesizes.h" 1 3 4
# 130 "/usr/include/bits/types.h" 2 3 4
__extension__ typedef unsigned long long int __dev_t;
__extension__ typedef unsigned int __uid_t;
__extension__ typedef unsigned int __gid_t;
__extension__ typedef unsigned long int __ino_t;
__extension__ typedef unsigned long long int __ino64_t;
__extension__ typedef unsigned int __mode_t;
__extension__ typedef unsigned int __nlink_t;
__extension__ typedef long int __off_t;
__extension__ typedef long long int __off64_t;
__extension__ typedef int __pid_t;
__extension__ typedef struct { int __val[2]; } __fsid_t;
__extension__ typedef long int __clock_t;
__extension__ typedef unsigned long int __rlim_t;
__extension__ typedef unsigned long long int __rlim64_t;
__extension__ typedef unsigned int __id_t;
__extension__ typedef long int __time_t;
__extension__ typedef unsigned int __useconds_t;
__extension__ typedef long int __suseconds_t;
__extension__ typedef int __daddr_t;
__extension__ typedef long int __swblk_t;
__extension__ typedef int __key_t;
__extension__ typedef int __clockid_t;
__extension__ typedef int __timer_t;
__extension__ typedef long int __blksize_t;
__extension__ typedef long int __blkcnt_t;
__extension__ typedef long long int __blkcnt64_t;
__extension__ typedef unsigned long int __fsblkcnt_t;
__extension__ typedef unsigned long long int __fsblkcnt64_t;
__extension__ typedef unsigned long int __fsfilcnt_t;
__extension__ typedef unsigned long long int __fsfilcnt64_t;
__extension__ typedef int __ssize_t;
typedef __off64_t __loff_t;
typedef __quad_t *__qaddr_t;
typedef char *__caddr_t;
__extension__ typedef int __intptr_t;
__extension__ typedef unsigned int __socklen_t;
# 37 "/usr/include/stdio.h" 2 3 4
typedef struct _IO_FILE FILE;
# 62 "/usr/include/stdio.h" 3 4
typedef struct _IO_FILE __FILE;
# 72 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/libio.h" 1 3 4
# 32 "/usr/include/libio.h" 3 4
# 1 "/usr/include/_G_config.h" 1 3 4
# 14 "/usr/include/_G_config.h" 3 4
# 1 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 1 3 4
# 325 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 3 4
typedef long int wchar_t;
# 354 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 3 4
typedef unsigned int wint_t;
# 15 "/usr/include/_G_config.h" 2 3 4
# 24 "/usr/include/_G_config.h" 3 4
# 1 "/usr/include/wchar.h" 1 3 4
# 48 "/usr/include/wchar.h" 3 4
# 1 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 1 3 4
# 49 "/usr/include/wchar.h" 2 3 4
# 1 "/usr/include/bits/wchar.h" 1 3 4
# 51 "/usr/include/wchar.h" 2 3 4
# 76 "/usr/include/wchar.h" 3 4
typedef struct
{
int __count;
union
{
wint_t __wch;
char __wchb[4];
} __value;
} __mbstate_t;
# 25 "/usr/include/_G_config.h" 2 3 4
typedef struct
{
__off_t __pos;
__mbstate_t __state;
} _G_fpos_t;
typedef struct
{
__off64_t __pos;
__mbstate_t __state;
} _G_fpos64_t;
# 44 "/usr/include/_G_config.h" 3 4
# 1 "/usr/include/gconv.h" 1 3 4
# 28 "/usr/include/gconv.h" 3 4
# 1 "/usr/include/wchar.h" 1 3 4
# 48 "/usr/include/wchar.h" 3 4
# 1 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 1 3 4
# 49 "/usr/include/wchar.h" 2 3 4
# 29 "/usr/include/gconv.h" 2 3 4
# 1 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stddef.h" 1 3 4
# 32 "/usr/include/gconv.h" 2 3 4
enum
{
__GCONV_OK = 0,
__GCONV_NOCONV,
__GCONV_NODB,
__GCONV_NOMEM,
__GCONV_EMPTY_INPUT,
__GCONV_FULL_OUTPUT,
__GCONV_ILLEGAL_INPUT,
__GCONV_INCOMPLETE_INPUT,
__GCONV_ILLEGAL_DESCRIPTOR,
__GCONV_INTERNAL_ERROR
};
enum
{
__GCONV_IS_LAST = 0x0001,
__GCONV_IGNORE_ERRORS = 0x0002
};
struct __gconv_step;
struct __gconv_step_data;
struct __gconv_loaded_object;
struct __gconv_trans_data;
typedef int (*__gconv_fct) (struct __gconv_step *, struct __gconv_step_data *,
__const unsigned char **, __const unsigned char *,
unsigned char **, size_t *, int, int);
typedef wint_t (*__gconv_btowc_fct) (struct __gconv_step *, unsigned char);
typedef int (*__gconv_init_fct) (struct __gconv_step *);
typedef void (*__gconv_end_fct) (struct __gconv_step *);
typedef int (*__gconv_trans_fct) (struct __gconv_step *,
struct __gconv_step_data *, void *,
__const unsigned char *,
__const unsigned char **,
__const unsigned char *, unsigned char **,
size_t *);
typedef int (*__gconv_trans_context_fct) (void *, __const unsigned char *,
__const unsigned char *,
unsigned char *, unsigned char *);
typedef int (*__gconv_trans_query_fct) (__const char *, __const char ***,
size_t *);
typedef int (*__gconv_trans_init_fct) (void **, const char *);
typedef void (*__gconv_trans_end_fct) (void *);
struct __gconv_trans_data
{
__gconv_trans_fct __trans_fct;
__gconv_trans_context_fct __trans_context_fct;
__gconv_trans_end_fct __trans_end_fct;
void *__data;
struct __gconv_trans_data *__next;
};
struct __gconv_step
{
struct __gconv_loaded_object *__shlib_handle;
__const char *__modname;
int __counter;
char *__from_name;
char *__to_name;
__gconv_fct __fct;
__gconv_btowc_fct __btowc_fct;
__gconv_init_fct __init_fct;
__gconv_end_fct __end_fct;
int __min_needed_from;
int __max_needed_from;
int __min_needed_to;
int __max_needed_to;
int __stateful;
void *__data;
};
struct __gconv_step_data
{
unsigned char *__outbuf;
unsigned char *__outbufend;
int __flags;
int __invocation_counter;
int __internal_use;
__mbstate_t *__statep;
__mbstate_t __state;
struct __gconv_trans_data *__trans;
};
typedef struct __gconv_info
{
size_t __nsteps;
struct __gconv_step *__steps;
__extension__ struct __gconv_step_data __data [];
} *__gconv_t;
# 45 "/usr/include/_G_config.h" 2 3 4
typedef union
{
struct __gconv_info __cd;
struct
{
struct __gconv_info __cd;
struct __gconv_step_data __data;
} __combined;
} _G_iconv_t;
typedef int _G_int16_t __attribute__ ((__mode__ (__HI__)));
typedef int _G_int32_t __attribute__ ((__mode__ (__SI__)));
typedef unsigned int _G_uint16_t __attribute__ ((__mode__ (__HI__)));
typedef unsigned int _G_uint32_t __attribute__ ((__mode__ (__SI__)));
# 33 "/usr/include/libio.h" 2 3 4
# 53 "/usr/include/libio.h" 3 4
# 1 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stdarg.h" 1 3 4
# 43 "/usr/lib/gcc-lib/powerpc-linux/3.3.4/include/stdarg.h" 3 4
typedef __builtin_va_list __gnuc_va_list;
# 54 "/usr/include/libio.h" 2 3 4
# 163 "/usr/include/libio.h" 3 4
struct _IO_jump_t; struct _IO_FILE;
# 173 "/usr/include/libio.h" 3 4
typedef void _IO_lock_t;
struct _IO_marker {
struct _IO_marker *_next;
struct _IO_FILE *_sbuf;
int _pos;
# 196 "/usr/include/libio.h" 3 4
};
enum __codecvt_result
{
__codecvt_ok,
__codecvt_partial,
__codecvt_error,
__codecvt_noconv
};
# 264 "/usr/include/libio.h" 3 4
struct _IO_FILE {
int _flags;
char* _IO_read_ptr;
char* _IO_read_end;
char* _IO_read_base;
char* _IO_write_base;
char* _IO_write_ptr;
char* _IO_write_end;
char* _IO_buf_base;
char* _IO_buf_end;
char *_IO_save_base;
char *_IO_backup_base;
char *_IO_save_end;
struct _IO_marker *_markers;
struct _IO_FILE *_chain;
int _fileno;
int _flags2;
__off_t _old_offset;
unsigned short _cur_column;
signed char _vtable_offset;
char _shortbuf[1];
_IO_lock_t *_lock;
# 312 "/usr/include/libio.h" 3 4
__off64_t _offset;
void *__pad1;
void *__pad2;
int _mode;
char _unused2[15 * sizeof (int) - 2 * sizeof (void *)];
};
typedef struct _IO_FILE _IO_FILE;
struct _IO_FILE_plus;
extern struct _IO_FILE_plus _IO_2_1_stdin_;
extern struct _IO_FILE_plus _IO_2_1_stdout_;
extern struct _IO_FILE_plus _IO_2_1_stderr_;
# 351 "/usr/include/libio.h" 3 4
typedef __ssize_t __io_read_fn (void *__cookie, char *__buf, size_t __nbytes);
typedef __ssize_t __io_write_fn (void *__cookie, __const char *__buf,
size_t __n);
typedef int __io_seek_fn (void *__cookie, __off64_t *__pos, int __w);
typedef int __io_close_fn (void *__cookie);
# 403 "/usr/include/libio.h" 3 4
extern int __underflow (_IO_FILE *) ;
extern int __uflow (_IO_FILE *) ;
extern int __overflow (_IO_FILE *, int) ;
extern wint_t __wunderflow (_IO_FILE *) ;
extern wint_t __wuflow (_IO_FILE *) ;
extern wint_t __woverflow (_IO_FILE *, wint_t) ;
# 433 "/usr/include/libio.h" 3 4
extern int _IO_getc (_IO_FILE *__fp) ;
extern int _IO_putc (int __c, _IO_FILE *__fp) ;
extern int _IO_feof (_IO_FILE *__fp) ;
extern int _IO_ferror (_IO_FILE *__fp) ;
extern int _IO_peekc_locked (_IO_FILE *__fp) ;
extern void _IO_flockfile (_IO_FILE *) ;
extern void _IO_funlockfile (_IO_FILE *) ;
extern int _IO_ftrylockfile (_IO_FILE *) ;
# 463 "/usr/include/libio.h" 3 4
extern int _IO_vfscanf (_IO_FILE * __restrict, const char * __restrict,
__gnuc_va_list, int *__restrict) ;
extern int _IO_vfprintf (_IO_FILE *__restrict, const char *__restrict,
__gnuc_va_list) ;
extern __ssize_t _IO_padn (_IO_FILE *, int, __ssize_t) ;
extern size_t _IO_sgetn (_IO_FILE *, void *, size_t) ;
extern __off64_t _IO_seekoff (_IO_FILE *, __off64_t, int, int) ;
extern __off64_t _IO_seekpos (_IO_FILE *, __off64_t, int) ;
extern void _IO_free_backup_area (_IO_FILE *) ;
# 73 "/usr/include/stdio.h" 2 3 4
# 86 "/usr/include/stdio.h" 3 4
typedef _G_fpos_t fpos_t;
# 138 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/bits/stdio_lim.h" 1 3 4
# 139 "/usr/include/stdio.h" 2 3 4
extern struct _IO_FILE *stdin;
extern struct _IO_FILE *stdout;
extern struct _IO_FILE *stderr;
extern int remove (__const char *__filename) ;
extern int rename (__const char *__old, __const char *__new) ;
extern FILE *tmpfile (void);
# 178 "/usr/include/stdio.h" 3 4
extern char *tmpnam (char *__s) ;
extern char *tmpnam_r (char *__s) ;
# 196 "/usr/include/stdio.h" 3 4
extern char *tempnam (__const char *__dir, __const char *__pfx)
__attribute__ ((__malloc__));
extern int fclose (FILE *__stream);
extern int fflush (FILE *__stream);
# 221 "/usr/include/stdio.h" 3 4
extern int fflush_unlocked (FILE *__stream);
# 235 "/usr/include/stdio.h" 3 4
extern FILE *fopen (__const char *__restrict __filename,
__const char *__restrict __modes);
extern FILE *freopen (__const char *__restrict __filename,
__const char *__restrict __modes,
FILE *__restrict __stream);
# 262 "/usr/include/stdio.h" 3 4
# 273 "/usr/include/stdio.h" 3 4
extern FILE *fdopen (int __fd, __const char *__modes) ;
# 294 "/usr/include/stdio.h" 3 4
extern void setbuf (FILE *__restrict __stream, char *__restrict __buf) ;
extern int setvbuf (FILE *__restrict __stream, char *__restrict __buf,
int __modes, size_t __n) ;
extern void setbuffer (FILE *__restrict __stream, char *__restrict __buf,
size_t __size) ;
extern void setlinebuf (FILE *__stream) ;
extern int fprintf (FILE *__restrict __stream,
__const char *__restrict __format, ...);
extern int printf (__const char *__restrict __format, ...);
extern int sprintf (char *__restrict __s,
__const char *__restrict __format, ...) ;
extern int vfprintf (FILE *__restrict __s, __const char *__restrict __format,
__gnuc_va_list __arg);
extern int vprintf (__const char *__restrict __format, __gnuc_va_list __arg);
extern int vsprintf (char *__restrict __s, __const char *__restrict __format,
__gnuc_va_list __arg) ;
extern int snprintf (char *__restrict __s, size_t __maxlen,
__const char *__restrict __format, ...)
__attribute__ ((__format__ (__printf__, 3, 4)));
extern int vsnprintf (char *__restrict __s, size_t __maxlen,
__const char *__restrict __format, __gnuc_va_list __arg)
__attribute__ ((__format__ (__printf__, 3, 0)));
# 388 "/usr/include/stdio.h" 3 4
extern int fscanf (FILE *__restrict __stream,
__const char *__restrict __format, ...);
extern int scanf (__const char *__restrict __format, ...);
extern int sscanf (__const char *__restrict __s,
__const char *__restrict __format, ...) ;
# 430 "/usr/include/stdio.h" 3 4
extern int fgetc (FILE *__stream);
extern int getc (FILE *__stream);
extern int getchar (void);
# 454 "/usr/include/stdio.h" 3 4
extern int getc_unlocked (FILE *__stream);
extern int getchar_unlocked (void);
# 465 "/usr/include/stdio.h" 3 4
extern int fgetc_unlocked (FILE *__stream);
extern int fputc (int __c, FILE *__stream);
extern int putc (int __c, FILE *__stream);
extern int putchar (int __c);
# 498 "/usr/include/stdio.h" 3 4
extern int fputc_unlocked (int __c, FILE *__stream);
extern int putc_unlocked (int __c, FILE *__stream);
extern int putchar_unlocked (int __c);
extern int getw (FILE *__stream);
extern int putw (int __w, FILE *__stream);
extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream);
extern char *gets (char *__s);
# 578 "/usr/include/stdio.h" 3 4
extern int fputs (__const char *__restrict __s, FILE *__restrict __stream);
extern int puts (__const char *__s);
extern int ungetc (int __c, FILE *__stream);
extern size_t fread (void *__restrict __ptr, size_t __size,
size_t __n, FILE *__restrict __stream);
extern size_t fwrite (__const void *__restrict __ptr, size_t __size,
size_t __n, FILE *__restrict __s);
# 631 "/usr/include/stdio.h" 3 4
extern size_t fread_unlocked (void *__restrict __ptr, size_t __size,
size_t __n, FILE *__restrict __stream);
extern size_t fwrite_unlocked (__const void *__restrict __ptr, size_t __size,
size_t __n, FILE *__restrict __stream);
extern int fseek (FILE *__stream, long int __off, int __whence);
extern long int ftell (FILE *__stream);
extern void rewind (FILE *__stream);
# 686 "/usr/include/stdio.h" 3 4
extern int fgetpos (FILE *__restrict __stream, fpos_t *__restrict __pos);
extern int fsetpos (FILE *__stream, __const fpos_t *__pos);
# 709 "/usr/include/stdio.h" 3 4
# 718 "/usr/include/stdio.h" 3 4
extern void clearerr (FILE *__stream) ;
extern int feof (FILE *__stream) ;
extern int ferror (FILE *__stream) ;
extern void clearerr_unlocked (FILE *__stream) ;
extern int feof_unlocked (FILE *__stream) ;
extern int ferror_unlocked (FILE *__stream) ;
extern void perror (__const char *__s);
# 1 "/usr/include/bits/sys_errlist.h" 1 3 4
# 27 "/usr/include/bits/sys_errlist.h" 3 4
extern int sys_nerr;
extern __const char *__const sys_errlist[];
# 748 "/usr/include/stdio.h" 2 3 4
extern int fileno (FILE *__stream) ;
extern int fileno_unlocked (FILE *__stream) ;
# 767 "/usr/include/stdio.h" 3 4
extern FILE *popen (__const char *__command, __const char *__modes);
extern int pclose (FILE *__stream);
extern char *ctermid (char *__s) ;
# 807 "/usr/include/stdio.h" 3 4
extern void flockfile (FILE *__stream) ;
extern int ftrylockfile (FILE *__stream) ;
extern void funlockfile (FILE *__stream) ;
# 831 "/usr/include/stdio.h" 3 4
# 2 "pp.c" 2
main(){
char c=-1;
if(c < 0){
printf("hola\n");
}
}
Thank You!!
--
Summary: Apparent bug in char comparison
Product: gcc
Version: 3.3.4
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: maizquierdop at unal dot edu dot co
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20464
