From: David Herrmann <dh.herrmann@gmail.com>
Date: Thu, 12 Jun 2014 15:54:48 +0000 (+0200)
Subject: macro: add DISABLE_WARNING_SHADOW
X-Git-Tag: v215~412
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=d442e2ec6e896c312bc616be7607332d978a45c9

macro: add DISABLE_WARNING_SHADOW

As it turns out, we cannot use _Pragma in compound-statements. Therefore,
constructs like MIN(MAX(a, b), x) will warn due to shadowed variable
declarations. The DISABLE_WARNING_SHADOW macro can be used to suppress
these.

Note that using UNIQUE(_var) does not work either as GCC uses the last
line of a macro-expansion for __LINE__, therefore, still causing both
macros to have the same variables. We could use different variable-names
for MIN and MAX, but that just hides the problem and still fails for
MIN(something(MIN(a, b)), c).

The only working solution is to use __COUNTER__ and pass it pre-evaluated
as extra argument to a macro to use as name-prefix. This, however, makes
all these macros much more complicated so I'll go with manual
DISABLE_WARNING_SHADOW so far.
---

diff --git a/src/shared/macro.h b/src/shared/macro.h
index 53bd578d7..32cf71485 100644
--- a/src/shared/macro.h
+++ b/src/shared/macro.h
@@ -63,6 +63,10 @@
         _Pragma("GCC diagnostic push");                                 \
         _Pragma("GCC diagnostic ignored \"-Wnonnull\"")
 
+#define DISABLE_WARNING_SHADOW                                          \
+        _Pragma("GCC diagnostic push");                                 \
+        _Pragma("GCC diagnostic ignored \"-Wshadow\"")
+
 #define REENABLE_WARNING                                                \
         _Pragma("GCC diagnostic pop")