Improve Assert output

[Peter Eisentraut]

This kind of output is usually not helpful:

TRAP: BadArgument("((context) != ((void *)0) && (((((const
Node*)((context)))->type) == T_AllocSetContext) || ((((const
Node*)((context)))->type) == T_SlabContext) || ((((const
Node*)((context)))->type) == T_GenerationContext)))", File:
"../../../../src/include/utils/memutils.h", Line: 129)

What we probably want is something like:

TRAP: BadArgument("MemoryContextIsValid(context)", File:
"../../../../src/include/utils/memutils.h", Line: 129)

The problem is that the way the Assert macros are written they
macro-expand the arguments before stringifying them.  The attached patch
fixes that.  This requires both replacing CppAsString by plain "#" and
not redirecting Assert() to Trap().

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

From 7db60e612e1d26c7a1859948594c28dc3b54353e Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Wed, 14 Aug 2019 22:23:34 +0200
Subject: [PATCH] Improve Assert output

If an assertion expression contained a macro, the failed assertion
message would print the expanded macro, which is usually unhelpful and
confusing.  Restructure the Assert macros to not expand any macros
when constructing the failure message.
---
 src/include/c.h | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/include/c.h b/src/include/c.h
index 2a082afab1..f461628a24 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -755,7 +755,7 @@ typedef NameData *Name;
 #define Trap(condition, errorType) \
        do { \
                if (condition) \
-                       ExceptionalCondition(CppAsString(condition), 
(errorType), \
+                       ExceptionalCondition(#condition, (errorType), \
                                                                 __FILE__, 
__LINE__); \
        } while (0)
 
@@ -768,20 +768,34 @@ typedef NameData *Name;
  */
 #define TrapMacro(condition, errorType) \
        ((bool) (! (condition) || \
-                        (ExceptionalCondition(CppAsString(condition), 
(errorType), \
+                        (ExceptionalCondition(#condition, (errorType), \
                                                                   __FILE__, 
__LINE__), 0)))
 
 #define Assert(condition) \
-               Trap(!(condition), "FailedAssertion")
+       do { \
+               if (!(condition)) \
+                       ExceptionalCondition(#condition, "FailedAssertion", \
+                                                                __FILE__, 
__LINE__); \
+       } while (0)
 
 #define AssertMacro(condition) \
-               ((void) TrapMacro(!(condition), "FailedAssertion"))
+       ((void) ((condition) || \
+                        (ExceptionalCondition(#condition, "FailedAssertion", \
+                                                                  __FILE__, 
__LINE__), 0)))
 
 #define AssertArg(condition) \
-               Trap(!(condition), "BadArgument")
+       do { \
+               if (!(condition)) \
+                       ExceptionalCondition(#condition, "BadArgument", \
+                                                                __FILE__, 
__LINE__); \
+       } while (0)
 
 #define AssertState(condition) \
-               Trap(!(condition), "BadState")
+       do { \
+               if (!(condition)) \
+                       ExceptionalCondition(#condition, "BadState", \
+                                                                __FILE__, 
__LINE__); \
+       } while (0)
 
 /*
  * Check that `ptr' is `bndr' aligned.
-- 
2.22.0