Al Viro wrote: > On Fri, Aug 03, 2007 at 12:51:16AM +0200, Guennadi Liakhovetski wrote: >> On Fri, 3 Aug 2007, Stefan Richter wrote: >> >>> Guennadi Liakhovetski wrote: >>>> with >>>> >>>> char c[4] = "012345"; >>>> >>>> the compiler warns, but actually allocates a 6-byte long array... >>> Off-topic here, but: sizeof c / sizeof *c == 4. >> Don't think it is OT here - kernel depends on gcc. And, what I meant, is, >> that gcc places all 7 (sorry, not 6 as I said above) characters in the >> .rodata section of the compiled object file. Of course, it doesn't mean, >> that c is 7 characters long. > > So gcc does that kind of recovery, after having warned you. Makes sense, > as long as it's for ordinary variables (and not, say it, struct fields) - > you get less likely runtime breakage on the undefined behaviour (e.g. > passing c to string functions). So gcc has generated some padding between > the global variables, that's all.
No, the fact that the full 012345\0 ends up in the object file is apparently unrelated to what happens to the variable c... > It doesn't change the fact that use of c[4] or strlen(c) or strcpy(..., c) > means nasal demon country for you. > > Now, if gcc does that for similar situation with struct fields, you'd have > a cause to complain. ...since only 0123 will get into c at runtime, i.e. a 4 bytes long array without \0 appendix or other extraordinary padding. #include <stdio.h> #include <string.h> int main() { char c[4] = "012345"; printf("%d %d _%s_\n", sizeof c / sizeof *c, strlen(c), c); return 0; } $ ./a.out 4 8 _01230®¿_ $ strings a.out |grep 0123 012345 -- Stefan Richter -=====-=-=== =--- ---== http://arcgraph.de/sr/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/