Subj : Htick Hatching
To   : andrew clarke
From : Michael Dukelsky
Date : Fri Mar 12 2021 15:29:34

Hello andrew,

Friday March 12 2021, andrew clarke wrote to Michael Dukelsky:

 PH>>>>> double free or corruption (fasttop)
 PH>>>>> Aborted

 ac>>> This is likely due to free() being called twice on the same
 ac>>> pointer somewhere in the Linux build of HTick.

 MD>> OK, thank you. It should be easy to fix.

 ac> nfree() may help but it's not foolproof. Consider this:

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

 ac> #define nfree(a) {if(a != NULL) {free(a); a = NULL;}}

 ac> static void foo(char *p)
 ac> {
 ac>     printf("%s\n", p);
 ac>     nfree(p);
 ac> }

 ac> int main(void)
 ac> {
 ac>     char *p = malloc(42);
 ac>     strcpy(p, "Hello!");
 ac>     foo(p);
 ac>     nfree(p);
 ac>     return 0;
 ac> }

 ac> Here foo() can only set its local copy of p to NULL. It can't modify
 ac> the original pointer.

 ac> There's not really any way around this kind of mistake in C, other
 ac> than to run it through a debugger, examine the code and fix it by
 ac> hand.

We'll wait for Paul to test it.

Michael

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