From: jsturm@sigma6.com (Jeff Sturm) Subject: Re: BUG in function parameter passing ?????? 29 Aug 1998 00:58:13 -0700 Message-ID: <35E6BE10.12F2CBD9.cygnus.gnu-win32@sigma6.com> References: <98082711213612@psicla.psi.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: Charles G Waldman Cc: Mark.Koennecke@psi.ch, gnu-win32@cygnus.com Charles G Waldman wrote: > > Mark.Koennecke@psi.ch writes: > > > > int main(int argc, char *argv[]) > > { > > char pBuffer[132]; > > > > /* why does this work? */ > > strcpy(pBuffer,"Hello You"); > > strtolower(pBuffer); > > > > /* but this gives a segmentation violation under Cygwin*/ > > strtolower("Hello You"); > > > > Because the string "Hello You" is a constant, and is allocated in the > read-only segment of the executable. The buffer pBuffer is allocated > read/write. This is done so that storage for literal strings can be > shared between object files. It's also for sharing string constants within an object file. If you compile the example with -fwritable-strings the constant "Hello You" will appear twice, otherwise just once. Modifying string constants is bad programming style and forbidden by the C spec, I think. I don't understand why gcc -Wall doesn't emit a warning when assigning a string constant to a non-constant parameter. This code fragment will emit a warning on the 2nd call to strtolower(), but no the first: int main(void) { const char *c = "Hello You"; strtolower("Hello You"); /* no warning */ strtolower(c); /* gcc warns here */ } -- Jeff Sturm jsturm@sigma6.com - For help on using this list (especially unsubscribing), send a message to "gnu-win32-request@cygnus.com" with one line of text: "help".