what does printing "%p" do?

Question

I have a linked-list. I want to put the current ptr sBuffer

each link is :

typedef struct{
   SearchContext *context;
   void *history;
   char id[32];
}ContextmenuContext;

but instead I'm getting the address of the next link.

I think "%p" is the bug.

what does printing "%p" do?

snprintf_safe(sBuffer,"%p",((ContextmenuContext*)current)->history);

print address, `%p` is a format string to print address, btw typecase to `void*` to use `%p` — Grijesh Chauhan, Oct 22 '13 at 13:30
You need to pass a `void*` for `%p` otherwise it's undefined behaviour. — Simple, Oct 22 '13 at 13:43
@Simple I think (hope) a `void const*` would work as well. But he is passing a `void*`, so that shouldn't be problem. (And this question should be labeled C, since it has nothing to do with C++.) — James Kanze, Oct 22 '13 at 13:55
@JamesKanze ah you're right. I just saw the cast and didn't look at the rest. — Simple, Oct 22 '13 at 15:02

score 4 · Accepted Answer · answered Oct 22 '13 at 13:31

4

%p is intended to display the pointer address.

answered Oct 22 '13 at 13:31

Arnaud Denoyelle

Note that that page contains a number of errors with regards to the types you pass to `printf`, depending on the specifiers. – James Kanze Oct 22 '13 at 13:54
See [`printf()` syntax](http://pubs.opengroup.org/onlinepubs/9699919799/functions/printf.html) according to POSIX. – This isn't my real name Oct 22 '13 at 16:43
@ElchononEdelson Posix has several extensions, and using the `printf` of Posix is likely to cause portability problems down the road, when you port to Windows. – James Kanze Oct 22 '13 at 16:53
@JamesKanze You'll have problems with `printf()` anyway, when you port to Windows. Doesn't windows discourage all sorts of normal C library functions in favor of proprietary versions? But note that POSIX is strongly aligned with the ISO C standard, and the POSIX documentation is very, _very_ clear about what comes from C and what is an extension. – This isn't my real name Oct 22 '13 at 16:56
@ElchononEdelson Not in favor of proprietary versions, but in favor of those defined in Annex K of the C standard. This is one case where it is Unix which tries to lock you into their extensions. (And the format specifiers for `printf` _do_ have significant extensions in Unix.) – James Kanze Oct 22 '13 at 17:32

1 Answers1