[PATCH v2] git_fopen: fix a sparse 'not declared' warning

From: Ramsay Jones <ramsay@ramsayjones.plus.com>
Date: May 8, 2017, 20:45 UTC
Message-ID: <2bf7d61e-c70f-a033-5cb2-2a66ac6fe459@ramsayjones.plus.com>

If git is built with the FREAD_READS_DIRECTORIES build variable set, this would cause sparse to issue a 'not declared, should it be static?' warning on Linux. This is a result of the method employed by 'compat/fopen.c' to suppress the (possible) redefinition of the (system) fopen macro, which also removes the extern declaration of the git_fopen function.

In order to suppress the warning, introduce a new macro to suppress the definition (or possibly the re-definition) of the fopen symbol as a macro override. This new macro (SUPPRESS_FOPEN_REDEFINITION) is only defined in 'compat/fopen.c', just prior to the inclusion of the 'git-compat-util.h' header file.

Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
---

Hi Junio,

I noticed the "What's cooking" entry for Duy's 'nd/fopen-errors' branch 'needs to resurrect' this patch, so I re-worded the commit message (because commit 8f4f6e53d2 is no more ...) so that it could stand alone. (or on the new re-rolled branch).

Thanks.

ATB, Ramsay Jones

 compat/fopen.c    |  4 ++--
 git-compat-util.h | 10 ++++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/compat/fopen.c b/compat/fopen.c
index b5ca142fe..107b3e818 100644
--- a/compat/fopen.c
+++ b/compat/fopen.c
@@ -1,14 +1,14 @@
 /*
  *  The order of the following two lines is important.
  *
- *  FREAD_READS_DIRECTORIES is undefined before including git-compat-util.h
+ *  SUPPRESS_FOPEN_REDEFINITION is defined before including git-compat-util.h
  *  to avoid the redefinition of fopen within git-compat-util.h. This is
  *  necessary since fopen is a macro on some platforms which may be set
  *  based on compiler options. For example, on AIX fopen is set to fopen64
  *  when _LARGE_FILES is defined. The previous technique of merely undefining
  *  fopen after including git-compat-util.h is inadequate in this case.
  */
-#undef FREAD_READS_DIRECTORIES
+#define SUPPRESS_FOPEN_REDEFINITION
 #include "../git-compat-util.h"
 
 FILE *git_fopen(const char *path, const char *mode)
diff --git a/git-compat-util.h b/git-compat-util.h
index df7b41524..33e06cac1 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -694,10 +694,12 @@ char *gitstrdup(const char *s);
 #endif
 
 #ifdef FREAD_READS_DIRECTORIES
-#ifdef fopen
-#undef fopen
-#endif
-#define fopen(a,b) git_fopen(a,b)
+# if !defined(SUPPRESS_FOPEN_REDEFINITION)
+#  ifdef fopen
+#   undef fopen
+#  endif
+#  define fopen(a,b) git_fopen(a,b)
+# endif
 extern FILE *git_fopen(const char*, const char*);
 #endif

-- 
2.12.0