Warnung bei printf und Addresseausgabe

Fabeltier

Hallo,
Beim kompilieren von dem Code unten, bekomme ich folgende warning:

warning: void format, different type arg (arg 3)

Dabei habe ich folgenden Code mit dem gcc und folgenden Flags compiliert:
-g -Wall -std=c99 -pedantic

Frage:
Warum bekomme ich hier eine Warnung und wie mache ich es richtig?
TIA

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define TEXT "foobar"

extern char* strcpy(char*, const char*);

int main(int argc, char** argv)
{
  int iStr_size = strlen(TEXT) + 1;
  char* pStr = NULL;
  if( (pStr = calloc(iStr_size, sizeof(*pStr))) == NULL) return EXIT_FAILURE;
  strcpy(pStr, TEXT);

  // void pointer
  void* pVoid;
  printf("init:\n\tiStr_size = %d\n\tpStr = \"%s\"\n", iStr_size, pStr);
  printf("\n");

  // pVoid -> int
  printf("init pVoid to int:\n");
  pVoid = (int*) &iStr_size;
  printf("\tpVoid = %p\tiStr_size = %p\n", pVoid, &iStr_size);  // WARNING?!
  printf("\tpVoid = %d\tiStr_size = %d\n", *((int*) pVoid), iStr_size);
  printf("\n");

  // free
  printf("free()\n");
  if(pStr != NULL) free(pStr);
  printf("READY.\n");

  return EXIT_SUCCESS;
}

supertux

Es ist nicht falsch, es liegt an der '-pedantic' Option (die meiner Meinung nach viel zu viel warnt). Die Warnung sagt

mist.c:24: warning: format '%p' expects type 'void *', but argument 3 has type 'int *'

Das dritte Argument ist nämlich "&iStr_size" und das ist ein int* und kein void*. Laut man: printf(3) erwartet "%p" einen void-Zeiger, darum die Warnung (die erst durch -pedantic angezeigt wird).

Fabeltier

Ja, so hab ich das auch irgendwie verstanden, aber wie macht man es denn "richtig"? Sollte ich hier etwa die Adresse der Intvariable auf einen dereferenzierten void* casten??
Irgendeinen Sinn muss diese Warnung doch haben, oder nicht?

supertux

es ist schon richtig, wie du es getan hast. Einen void* Cast, nur um den ISO C glückglich zu machen, finde ich nicht sinnvoll. Mein gcc man page meint zu -pedantic folgendes:

-pedantic
Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that use forbidden extensions, and some other programs
that do not follow ISO C and ISO C++. For ISO C, follows the version of the ISO C standard specified by any -std option used.

Valid ISO C and ISO C++ programs should compile properly with or without this option (though a rare few will require -ansi or a -std option
specifying the required version of ISO C). However, without this option, certain GNU extensions and traditional C and C++ features are
supported as well. With this option, they are rejected.

-pedantic does not cause warning messages for use of the alternate keywords whose names begin and end with __. Pedantic warnings are also
disabled in the expression that follows "__extension__". However, only system header files should use these escape routes; application
programs should avoid them.

**
Some users try to use -pedantic to check programs for strict ISO C conformance. They soon find that it does not do quite what they want:
it finds some non-ISO practices, but not all---only those for which ISO C requires a diagnostic, and some others for which diagnostics have
been added.
**

A feature to report any failure to conform to ISO C might be useful in some instances, but would require considerable additional work and
would be quite different from -pedantic. We don't have plans to support such a feature in the near future.

Where the standard specified with -std represents a GNU extended dialect of C, such as gnu89 or gnu99, there is a corresponding base stan-
dard, the version of ISO C on which the GNU extended dialect is based. Warnings from -pedantic are given where they are required by the
base standard. (It would not make sense for such warnings to be given only for features not in the specified GNU C dialect, since by defi-
nition the GNU dialects of C include all features the compiler supports with the given option, and there would be nothing to warn about.)

Wenn du strict ISO C conformance brauchst/benötigst/willst, dann musst du casten. Ich finde es an der Stelle sinnlos, selbst wenn es nicht strikt ISO C konform ist.

Fabeltier

Ok, ich gluab ich hab's begriffen -pedantic heisst wirklich "pedantisch"
Danke!