memory dellocation

[c.arnet]

Hi there,

I've written a function that 'converts' a structure of type timeval to
a c-string:

char *tv2Str(struct timeval tvX)
{
char caStr[20];
char *cpResult;

sprintf(caStr, "%ld.%ld", tvX.tv_sec, tvX.tv_usec);

cpResult = (char *)malloc(sizeof(char)*strlen(caStr));
strcpy(cpResult, caStr);

return cpResult;
}

I use it like this:

printf("%s", tv2Str((struct timeval){123, 456}) );

Question:
How (if at all) does the compiler (gcc) ensure that the memory
allocated in the above function is deallocated after the printf call ?

Thanks,
Cornel

 

[Richard Bos]

char *tv2Str(struct timeval tvX)
{
char *cpResult;

cpResult = (char *)malloc(sizeof(char)*strlen(caStr));

There's no need to cast malloc(). It returns a void *, which can be
assigned to any kind of object pointer without a cast. You _did_

return cpResult;
}

I use it like this:

printf("%s", tv2Str((struct timeval){123, 456}) );

How (if at all) does the compiler (gcc) ensure that the memory
allocated in the above function is deallocated after the printf call ?

It doesn't, so this is a bad way to call that function.

Richard

 

[j]

There's no need to cast malloc(). It returns a void *, which can be
assigned to any kind of object pointer without a cast.

_any_? What about a pointer to a function?

 

[Alan Balmer]

_any_? What about a pointer to a function?

Is a function an object?

 

[Neil Cerutti]

(e-mail address removed) (Richard Bos) wrote in message


_any_? What about a pointer to a function?

If it were possible to do, it would be useless.

#include <stdlib.h>
int main(void)
{
int (*pf)(void) = malloc(sizeof *pf); /* ??? */
*pf = main; /* ??? */
return EXIT_FAILURE;
}