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

[Tim Ruehsen]

On Thursday 20 November 2014 11:52:40 Darshit Shah wrote:
> On 11/19, Tim Rühsen wrote:
> >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.)
> 
> My question was. On systems where alloca.h is not available, this code has
> no fallback. If alloca.h is not included, then the
> 
> char *ca_file = alloca(ca_file_length);
> 
> line will prevent the source from compiling. Should be not have something to
> prevent that?

Sorry for being unclear. NOT having alloca.h means, alloca() is defined 
somewhere else, or it is even interpreted directly by the compiler. As long as 
you don't use -Werror, you will just see a warning when compiling.

Conclusion: I do not see a problem here. If you think there is, we should 
completely repair Wget. But this is a different issue. This patch will lean on 
the existing Wget standards.

> >I do not know systems without alloca() function.
> >Wget sources already use alloca on several places.
> 
> If Wget sources are already doing this, and no one has yet complained then
> it means we've probably not hit the case yet where someone tried to compile
> Wget on a system without alloca.h

That is not true, see above.

But I will amend the patch and remove #include <alloca.h>. I just saw, wget.h  
already includes it.

Tim

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