qobject atomics osdep: Make a few macros more hygienic

[mirror_qemu.git] / include / qemu / osdep.h

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index e4a4eb2d613527fca2accdf8e003609d102837a3..18b940db75852d955185835c5f3b2643aa3735df 100644 (file)
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -383,19 +383,28 @@ void QEMU_ERROR("code path is reachable")
  * determined by the pre-processor instead of the compiler, you'll
  * have to open-code it.  Sadly, Coverity is severely confused by the
  * constant variants, so we have to dumb things down there.
+ *
+ * Preprocessor sorcery ahead: use different identifiers for the local
+ * variables in each expansion, so we can nest macro calls without
+ * shadowing variables.
  */
-#undef MIN
-#define MIN(a, b)                                       \
+#define MIN_INTERNAL(a, b, _a, _b)                      \
     ({                                                  \
         typeof(1 ? (a) : (b)) _a = (a), _b = (b);       \
         _a < _b ? _a : _b;                              \
     })
-#undef MAX
-#define MAX(a, b)                                       \
+#undef MIN
+#define MIN(a, b) \
+    MIN_INTERNAL((a), (b), MAKE_IDENTFIER(_a), MAKE_IDENTFIER(_b))
+
+#define MAX_INTERNAL(a, b, _a, _b)                      \
     ({                                                  \
         typeof(1 ? (a) : (b)) _a = (a), _b = (b);       \
         _a > _b ? _a : _b;                              \
     })
+#undef MAX
+#define MAX(a, b) \
+    MAX_INTERNAL((a), (b), MAKE_IDENTFIER(_a), MAKE_IDENTFIER(_b))
 
 #ifdef __COVERITY__
 # define MIN_CONST(a, b) ((a) < (b) ? (a) : (b))
@@ -416,14 +425,18 @@ void QEMU_ERROR("code path is reachable")
 /*
  * Minimum function that returns zero only if both values are zero.
  * Intended for use with unsigned values only.
+ *
+ * Preprocessor sorcery ahead: use different identifiers for the local
+ * variables in each expansion, so we can nest macro calls without
+ * shadowing variables.
  */
-#ifndef MIN_NON_ZERO
-#define MIN_NON_ZERO(a, b)                              \
+#define MIN_NON_ZERO_INTERNAL(a, b, _a, _b)             \
     ({                                                  \
         typeof(1 ? (a) : (b)) _a = (a), _b = (b);       \
         _a == 0 ? _b : (_b == 0 || _b > _a) ? _a : _b;  \
     })
-#endif
+#define MIN_NON_ZERO(a, b) \
+    MIN_NON_ZERO_INTERNAL((a), (b), MAKE_IDENTFIER(_a), MAKE_IDENTFIER(_b))
 
 /*
  * Round number down to multiple. Safe when m is not a power of 2 (see