Re: [Bug-wget] [PATCH] Fixing C89 warnings

[Giuseppe Scrivano]

Tim Rühsen <address@hidden> writes:

> Am Mittwoch, 19. November 2014, 22:07:28 schrieb Darshit Shah:
>> On 11/18, Tim Rühsen wrote:
>> >This patch fixes most C89 warnings for me (-std=c89 -pedantic) since these
>> >may prevent from compiling with MSVC.
>> >
>> >There are still some warnings "ISO C forbids conversion of function pointer
>> >to object pointer type [-Wpedantic]" left over. I'll care for these the
>> >next days. There are architectures where function pointers have a
>> >different size from void *. That's why this warning has a meaning.
>> >
>> >Tim
>> >
>> >From 11baace21e1fa04a92baa395f38ebad8001e9762 Mon Sep 17 00:00:00 2001
>> >From: Tim Ruehsen <address@hidden>
>> >Date: Tue, 18 Nov 2014 22:00:48 +0100
>> >Subject: [PATCH] Trivial fixes for C89 compliancy.
>> 
>> <snip>
>> 
>> >diff --git a/src/gnutls.c b/src/gnutls.c
>> >index 87d1d0b..42201e5 100644
>> >--- a/src/gnutls.c
>> >+++ b/src/gnutls.c
>> >@@ -54,6 +54,10 @@ as that of the covered work.  */
>> >
>> > # include "w32sock.h"
>> > #endif
>> >
>> >+#ifdef HAVE_ALLOCA_H
>> >+# include <alloca.h>
>> >+#endif
>> >+
>> >
>> > #include "host.h"
>> > 
>> > static int
>> >
>> >@@ -122,9 +126,10 @@ ssl_init (void)
>> >
>> >           while ((dent = readdir (dir)) != NULL)
>> >           
>> >             {
>> >             
>> >               struct stat st;
>> >
>> >-              char ca_file[dirlen + strlen(dent->d_name) + 2];
>> >+              size_t ca_file_length = dirlen + strlen(dent->d_name) + 2;
>> >+              char *ca_file = alloca(ca_file_length);
>> 
>> What happens when HAVE_ALLOCA_H is not defined? The above code will attempt
>> to call a function that does not exist and Wget will crash.
>> 
>> I think, we can simply malloc / free() these. Sure alloca is more
>> convenient, but we need a valid fallback for when it is not available.
>
> There are systems without alloca.h header file. Thus the check.
> (I just had an error report for libpsl with this issue.)
>
> I do not know systems without alloca() function.
> Wget sources already use alloca on several places.

I also think we should simply use malloc/free instead of alloca (not
that it is worth a rewriting now) but in future let's not add more
instances of it.  malloc is safer than alloca.

Regards,
Giuseppe