Warnings with gcc

[thibault.langlois]

Hello,
I get a warning when I compile:
#include <string.h>

int main (int argc, char ** argv)
{
char * s;
s = strdup("a string");
return 0;
}

with gcc (GCC) 3.3.5 (Debian 1:3.3.5-8ubuntu2) :

$ gcc -Wall -ansi warning.c
warning.c: In function `main':
warning.c:7: warning: implicit declaration of function `strdup'
warning.c:7: warning: assignment makes pointer from integer without a
cast

Does anybody knows how can I supress this warning ?

if I put a cast : s = (char *) strdup("a string");
I get another warning message:
warning.c:7: warning: implicit declaration of function `strdup'

I do not understand why this happens because strdup is declared in
string.h

Thanks,

Thibault Langlois

[rayw]

<th************ ***@di.fc.ul.pt > wrote in message
news:11******** **************@ g47g2000cwa.goo glegroups.com.. .

Hello,
I get a warning when I compile:
#include <string.h>

int main (int argc, char ** argv)
{
char * s;
s = strdup("a string");
return 0;
}

with gcc (GCC) 3.3.5 (Debian 1:3.3.5-8ubuntu2) :

$ gcc -Wall -ansi warning.c
warning.c: In function `main':
warning.c:7: warning: implicit declaration of function `strdup'
warning.c:7: warning: assignment makes pointer from integer without a
cast

Does anybody knows how can I supress this warning ?

if I put a cast : s = (char *) strdup("a string");
I get another warning message:
warning.c:7: warning: implicit declaration of function `strdup'

I do not understand why this happens because strdup is declared in
string.h

Well, it can't be can it - unless the compiler's wrong?

Have you confirmed that it's in [your] string.h?

Does your preprocessed output contain it?

Does it link?

rayw

[pete]

th************* **@di.fc.ul.pt wrote:

I do not understand why this happens because strdup is declared in
string.h

strdup is not in string.h

news:gnu.gcc

http://www.ungerhu.com/jxh/clc.welcome.txt

--
pete

[Richard Bos]

"th************ ***@di.fc.ul.pt " <th************ ***@di.fc.ul.pt > wrote:

I get a warning when I compile:
#include <string.h>

int main (int argc, char ** argv)
{
char * s;
s = strdup("a string");
return 0;
} warning.c:7: warning: implicit declaration of function `strdup'

I do not understand why this happens because strdup is declared in
string.h

strdup() is not ISO C, and should therefore _not_ be declared in
<string.h> in a conforming implementation. Looks like gcc with -ansi is
conforming in this respect (as in most, perhaps all, others).

Richard

[Robert Gamble]

th************* **@di.fc.ul.pt wrote:

Hello,
I get a warning when I compile:
#include <string.h>

int main (int argc, char ** argv)
this is better than int main () or void main (void) which we see too
often around here, but since you are not using either of these
variables, why not just int main (void)?
{
char * s;
s = strdup("a string");
strdup is not a Standard C function, it is a BSD extension. You
specified the -ansi option when you tried to compile this telling the
compiler you want to compile as a strictly conforming program. This
option defines the macro __STRICT_ANSI__ which will keep the prototype
for strdup from being visible from string.h. You can either remove the
-ansi switch, or place the following define before your include
directive:
#define _GNU_SOURCE
return 0;
}

with gcc (GCC) 3.3.5 (Debian 1:3.3.5-8ubuntu2) :

$ gcc -Wall -ansi warning.c
warning.c: In function `main':
warning.c:7: warning: implicit declaration of function `strdup'
The prototype for strdup is not in scope, hence the diagnostic, see
above.
warning.c:7: warning: assignment makes pointer from integer without a
cast
Since the prototype for strdup is not in scope, the compiler assumes it
returns an int which you are storing into a pointer without a cast,
this is required to produce a diagnostic.
Does anybody knows how can I supress this warning ?
The -w switch turns off all warnings but this justs hides the problem,
fix the issue instead.
if I put a cast : s = (char *) strdup("a string");
I get another warning message:
warning.c:7: warning: implicit declaration of function `strdup'

Since you cast the result of strdup, which the compiler thinks is an
int, to a char * a diagnostic is not required. You still have the
issue of strdup not being declared. If you are using a cast to supress
a compiler diagnostic, this is a good clue you are doing something
wrong.

Robert Gamble

[Barry]

<th************ ***@di.fc.ul.pt > wrote in message
news:11******** **************@ g47g2000cwa.goo glegroups.com.. .

Hello,
I get a warning when I compile:
#include <string.h>

int main (int argc, char ** argv)
{
char * s;
s = strdup("a string");
return 0;
}

with gcc (GCC) 3.3.5 (Debian 1:3.3.5-8ubuntu2) :

$ gcc -Wall -ansi warning.c
warning.c: In function `main':
warning.c:7: warning: implicit declaration of function `strdup'
warning.c:7: warning: assignment makes pointer from integer without a
cast

Does anybody knows how can I supress this warning ?

if I put a cast : s = (char *) strdup("a string");
I get another warning message:
warning.c:7: warning: implicit declaration of function `strdup'

I do not understand why this happens because strdup is declared in
string.h

Thanks,

Thibault Langlois

drop the "-ansi" strdup is a non-ANSI extension (at least according to gcc).

barry

[Skarmander]

Barry wrote:

<th************ ***@di.fc.ul.pt > wrote in message
news:11******** **************@ g47g2000cwa.goo glegroups.com.. .

I get a warning when I compile:
#include <string.h>

int main (int argc, char ** argv)
{
char * s;
s = strdup("a string");
return 0;
}

with gcc (GCC) 3.3.5 (Debian 1:3.3.5-8ubuntu2) :

$ gcc -Wall -ansi warning.c
warning.c: In function `main':
warning.c:7 : warning: implicit declaration of function `strdup'

<snip>
drop the "-ansi" strdup is a non-ANSI extension (at least according to gcc).

That's not quite it. gcc would in fact be allowed to provide strdup()
even in ANSI mode, but it chooses not to, presumably to help people
catch conformance errors (which is -ansi's primary purpose).

(To be even more precise, it actually depends on the standard library
implementation used with gcc.)

S.

[Barry]

"Skarmander " <in*****@dontma ilme.com> wrote in message
news:43******** *************** @news.xs4all.nl ...

Barry wrote:

<th************ ***@di.fc.ul.pt > wrote in message
news:11******** **************@ g47g2000cwa.goo glegroups.com.. .

I get a warning when I compile:
#include <string.h>

int main (int argc, char ** argv)
{
char * s;
s = strdup("a string");
return 0;
}

with gcc (GCC) 3.3.5 (Debian 1:3.3.5-8ubuntu2) :

$ gcc -Wall -ansi warning.c
warning.c: In function `main':
warning.c:7 : warning: implicit declaration of function `strdup' <snip>

drop the "-ansi" strdup is a non-ANSI extension (at least according to

gcc).

That's not quite it. gcc would in fact be allowed to provide strdup()
even in ANSI mode, but it chooses not to, presumably to help people
catch conformance errors (which is -ansi's primary purpose).

(To be even more precise, it actually depends on the standard library
implementation used with gcc.)

S.

Thanks for the correction. My post was based solely on the comments in the
gcc
header files.

barry

[jacob navia]

pete wrote:

th************* **@di.fc.ul.pt wrote:

I do not understand why this happens because strdup is declared in
string.h

strdup is not in string.h

news:gnu.gcc

http://www.ungerhu.com/jxh/clc.welcome.txt

strdup is in string.h in my linux system with
gcc version 2.96 20000731 (Mandrake Linux 8.2 2.96-0.76mdk)

jacob

[Skarmander]

jacob navia wrote:

pete wrote:

th************* **@di.fc.ul.pt wrote:

I do not understand why this happens because strdup is declared in
string.h

strdup is not in string.h

news:gnu.gcc

http://www.ungerhu.com/jxh/clc.welcome.txt

strdup is in string.h in my linux system with
gcc version 2.96 20000731 (Mandrake Linux 8.2 2.96-0.76mdk)

strdup() is *not necessarily* in string.h. It's a nonstandard function;
the standard doesn't define it. Implementations are allowed to define
additional functions beginning with "str" in <string.h>, however (and if
<string.h> is included, a program may not define such functions).

S.