Package: gcc-4.9
Version: 4.9.0-6
$ cat t.c
#define _FORTIFY_SOURCE 2
#include <stdio.h>
#include <limits.h>
long long size;
void execute(void) {
unsigned char input[4096];
size_t bytes = (size > (ssize_t)sizeof input
? sizeof input
: size);
size_t bytesRead = fread(input, 1, bytes, stdin);
}
int main(int argc, char **argv) {
size = LLONG_MAX;
execute();
return 0;
}
$ gcc-4.9 -O2 t.c
$ gcc-4.9 -O2 -flto t.c
In function ‘__fread_alias’,
inlined from ‘execute’ at t.c:12:10:
/usr/include/i386-linux-gnu/bits/stdio2.h:290:2: warning: call to
‘__fread_chk_warn’ declared with attribute warning: fread called with
bigger size * nmemb than length of destination buffer
return __fread_chk (__ptr, __bos0 (__ptr), __size, __n, __stream);
^
richard@deodand:~/src/vbig$ dpkg -l libc6-dev gcc-4.9
Desired=Unknown/Install/Remove/Purge/Hold
|
Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-============-============-=================================
ii gcc-4.9 4.9.0-6 i386 GNU C compiler
ii libc6-dev:i386 2.19-1 i386 Embedded GNU C Library:
Developme
The relevant portion of stdio2.h is:
266 extern size_t __fread_chk (void *__restrict __ptr, size_t __ptrlen,
267 size_t __size, size_t __n,
268 FILE *__restrict __stream) __wur;
269 extern size_t __REDIRECT (__fread_alias,
270 (void *__restrict __ptr, size_t __size,
271 size_t __n, FILE *__restrict __stream),
272 fread) __wur;
273 extern size_t __REDIRECT (__fread_chk_warn,
274 (void *__restrict __ptr, size_t __ptrlen,
275 size_t __size, size_t __n,
276 FILE *__restrict __stream),
277 __fread_chk)
278 __wur __warnattr ("fread called with bigger size * nmemb
than length "
279 "of destination buffer");
280
281 __fortify_function __wur size_t
282 fread (void *__restrict __ptr, size_t __size, size_t __n,
283 FILE *__restrict __stream)
284 {
285 if (__bos0 (__ptr) != (size_t) -1)
286 {
287 if (!__builtin_constant_p (__size)
288 || !__builtin_constant_p (__n)
289 || (__size | __n) >= (((size_t) 1) << (8 * sizeof
(size_t) / 2)))
290 return __fread_chk (__ptr, __bos0 (__ptr), __size, __n,
__stream);
291
292 if (__size * __n > __bos0 (__ptr))
293 return __fread_chk_warn (__ptr, __bos0 (__ptr), __size,
__n, __stream);
294 }
295 return __fread_alias (__ptr, __size, __n, __stream);
296 }
The warning attribute is attached to __fread_chk_warn (called line 293)
but the warning is issued against line 290 where __fread_chk is called -
so the compiler has got confused about these two functions?
ttfn/rjk
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