Hi all, please consider this example from FFI::Platypus:


#include <string.h>
#include <stdlib.h>
 
const char *
string_reverse(const char *input)
{
  static char *output = NULL;
  int i, len;
 
  if(output != NULL)
    free(output);
 
  if(input == NULL)
    return NULL;
 
  len = strlen(input);
  output = malloc(len+1);
 
  for(i=0; input[i]; i++)
    output[len-i-1] = input[i];
  output[len] = '\0';
 
  return output;
}

[download]
use FFI::Platypus 2.00;
 
my $ffi = FFI::Platypus->new(
  api => 2,
  lib => './string_reverse.so',
);
 
$ffi->attach( string_reverse => ['string'] => 'string' );
 
print string_reverse("\nHello world");
 
string_reverse(undef);

[download]

Note the second call of string_reverse. From ibidem:

"At the end of the program we call reverse_string with undef, which gets translated to C as NULL. This allows it to free the output buffer so that the memory will not leak."

A smart aleck might jump to the conclusion to replace malloc with GC_MALLOC as described here.

Is this recommended or will it cause problems in the future not yet imaginable now?

Thanks for any hint and best regards, Karl

P.S.: See also Boehm–Demers–Weiser Garbage Collector

Update: Thank you all for the kind and very informative responses. I now consider this a research project for the future. So far I don't even know if the mentioned library compiles on the Mac. I will report back.

«The Crux of the Biscuit is the Apostrophe»

In reply to FFI::Platypus: Replace malloc with GC_MALLOC? by karlgoethebier

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