Shriramana Sharma writes: > Dear list, > > Namaste (hello). This is my first post. I wonder if I have found a bug or at > least an anomalous behaviour in GCC. Please download the file segfault.tar.gz > from: > > http://www.yousendit.com/transfer.php?action=download&ufid=0D3E9B791AE99BEA > > (available for seven days from now). Do make and test both monthpan and > monthpan-bug with any date range that contains a Sunday (which is where the > bug lies). You should find that monthpan creates an output file called > monthpan.txt whereas monthpan-bug creates a segmentation fault at > grahanaama[0] (grahanaama means "weekday name"). You call swe_fixstar with the argument 0 (star) = spicanaama. swe_fixstar does sprintf(star, "%s,%s", cpos[0], cpos[1]) so, it overwrites its input argument (spicanaama). But spicanaama isn't big enough to contain the resulting string, so it overwites the next variable, which is grahanaama[0]. > The only difference between the two source files monthpan.c and monthpan-bug.c > is that the latter contains the line: > > char spicanaama[] = "Spica"; > > *before* the start of the declarations of the two-dimensional arrays, which > for some reason seems to cause the zero element of the first two-dimensional > array to be out-of-bounds. > > This problem confirmed on gcc-4.1/glibc-2.4 and gcc-3.35/glibc-2.34. > > Please can anyone enlighten me as to what exactly causes this bug? Is it a bug > with GCC? If yes, where do I report it? Don't! Andrew.
