Re: [PATCH] Fix "identifier redeclared" compilation error with SUN cc

From: Guido Ostkamp <git@ostkamp.fastmail.fm>
Date: Nov 20, 2007, 17:28 UTC
Message-ID: <Pine.LNX.4.64.0711201823460.4280@bianca.dialin.t-online.de>
In-Reply-To: <7vhcjhl3ni.fsf@gitster.siamese.dyndns.org>

Hello Junio,

On Tue, 20 Nov 2007, Junio C Hamano wrote:

Show 14 quoted lines

> I knew it would work on Solaris with gcc and cc that do not understand 
> flexible array members, but I am a bit worried about other environments, 
> where flexible array members are properly supported.  They've been 
> happily using member[] but with the patch they suddenly start wasting a 
> cell.
>
> But we should do this sooner rather than later to find out any breakage, 
> and give people on platforms with a cc that supports flexible array 
> members and care about wasted memory enough time to send patches to 
> support their compiler in the way similar to how gcc is supported.
>
> But I cannot use your message with whitespace-broken patch (note 
> "format=flawed") and insufficient commit log message, which means I have 
> to do this myself.  Not tonight...

sorry for the whitespace-issues. I have attached the patch again with improved log message and will turn off format-flawed for this email.

Please let me know if this one is ok and feel free to fix it.

Log message starts here:

Fix "identifier redeclared" compilation error with SUN cc.

The problem is caused by incomplete arrays like

   struct foo {
     ...
     char last_member_that_is_flexible[];
   }

which cannot be handled by certain compilers. The solution is to change the last member to either

     char last_member_that_is_flexible[0]

or

     char last_member_that_is_flexible[1]

as required. Currently GNU CC can handle [] format for version 3 and later. Earlier versions need [0]. Non-GNU compiler use the safe form [1].

Signed-off-by: Guido Ostkamp <git@ostkamp.fastmail.fm>
---
  git-compat-util.h |   11 ++++++++++-
  1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index 276a437..97759fd 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -4,11 +4,20 @@
  #define _FILE_OFFSET_BITS 64

  #ifndef FLEX_ARRAY
-#if defined(__GNUC__) && (__GNUC__ < 3)
+#if defined(__GNUC__)
+#if (__GNUC__ < 3)
  #define FLEX_ARRAY 0
  #else
  #define FLEX_ARRAY /* empty */
  #endif
+#else
+/* more cases we know we can use 0 or empty can come here */
+#endif
+#endif
+
+/* if still undefined, default to the safe, old fashioned way */
+#ifndef FLEX_ARRAY
+#define FLEX_ARRAY 1
  #endif

  #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))

-- 
1.5.3.6.728.gea559