On Wed, Apr 23, 2008 at 02:19:53AM -0700, Garrett Cooper wrote: > On Wed, Apr 23, 2008 at 1:30 AM, Bernard van Gastel <[EMAIL PROTECTED]> > wrote: > > > > > Op 23 apr 2008, om 08:50 heeft Mike Meyer het volgende geschreven: > > > > > On Tue, 22 Apr 2008 22:40:21 -0700 > > > "Garrett Cooper" <[EMAIL PROTECTED]> wrote: > > > > > > Hi all, > > > > I made an oops in a program, which uncovered "feature" in strdup(2) > > > > that I wasn't aware of before. So I was wondering, is strdup(pointer = > > > > NULL) > > > > supposed to segfault should this just return NULL and set errno? > > > > > > > > > > Yes, it's supposed to segfault. Check out what, say, strcpy does if > > > you ask it to copy a NULL pointer. And this is an improvement from the > > > bad old days, when they would happily walk through memory starting at > > > 0..... > > > > > > > I don't like it this way. I would like: > > > > strdup(NULL) = NULL > > strdup(string) = copy of string > > > > strcpy(NULL, NULL) = NULL > > strcpy(s1, NULL) = ERROR > > strcpy(NULL, s2) = NULL (with s2 unchanged) > > strcpy(s1, s2) = normal > > > > But I am not sure of the implications. Maybe in some situation it is > > bad... Anyone? > > > > > > > Besides, errno is used to signal errors from system calls. strdup > > > isn't a system call, it's a library function (says so at the top of > > > the man page). > > > > > > > But strdup uses malloc, which is a system call (from the strdup manual: If > > insufficient memory is available, NULL is returned and errno is set to > > ENOMEM.) > > > > Regards, > > Bernard > > > > > I was more concerned about the fact that there wasn't any documentation that > said something -- either implicitly or explicitly -- that strdup(NULL) > causes a segfault. > > Of course I did some more research after you guys gave me some replies and > realized I'm not the first person to bumble across this fact, but I haven't > found FreeBSD or Linux documentation supporting that errata. It was harmless > in my tiny program, but I would hate to be someone adding that assumption to > a larger project with multiple threads and a fair number of lines... > > *shrugs*. > > -Garrett > > PS I'm as much against POLA changes as the next guy. I just don't like > shooting myself in the foot too terribly much :).
From the ISO/IEC 9899:1999 (E), 7.1.4, clause 1 Each of the following statements applies unless explicitly stated otherwise in the detailed descriptions that follow: If an argument to a function has an invalid value (such as a value outside the domain of the function, or a pointer outside the address space of the program, or a null pointer, or a pointer to non-modifiable storage when the corresponding parameter is not const-qualified) or a type (after promotion) not expected by a function with variable number of arguments, the behavior is undefined.
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