alloca()

Allocate automatic space from the stack

Synopsis:

#include <alloca.h>

void* alloca( size_t size );

Arguments:

size

The number of bytes of memory to allocate.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The alloca() function allocates space for an object of size bytes from the stack. The allocated space is automatically discarded when the current function exits.

Don't use this function in an expression that's an argument to a function.

Returns:

A pointer to the start of the allocated memory, or NULL if an error occurred (errno is set).

Examples:

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

FILE *open_err_file( char *name )
{
    char *buffer;

    /* allocate temporary buffer for file name */
    buffer = (char *)alloca( strlen( name ) + 5 );

    if( buffer ) {
        FILE *fp;

        sprintf( buffer, "%s.err", name );
        fp = fopen( buffer, "w" );

        return fp;
    }

    return (FILE *)NULL;
}

int main( void )
{
    FILE *fp;

    fp = open_err_file( "alloca_test" );
    if( fp == NULL ) {
        printf( "Unable to open error file\n" );
    } else {
        fprintf( fp, "Hello from the alloca test.\n" );
        fclose( fp );
    }

    return EXIT_SUCCESS;
}

Classification:

Unix

Caveats:

Don't use alloca() as an argument to a function.

See also:

calloc(), malloc()