Change return type of ExceptionalCondition to void and mark it noreturn

In ancient times, it was thought that this wouldn't work because of
TrapMacro/AssertMacro, but changing those to use a comma operator
appears to work without compiler warnings.

src/backend/utils/error/assert.c

@@ -21,11 +21,8 @@
 
 /*
  * ExceptionalCondition - Handles the failure of an Assert()
- *
- * Note: this can't actually return, but we declare it as returning int
- * because the TrapMacro() macro might get wonky otherwise.
  */
-int
+void
 ExceptionalCondition(const char *conditionName,
 					 const char *errorType,
 					 const char *fileName,
@@ -55,6 +52,4 @@ ExceptionalCondition(const char *conditionName,
 #endif
 
 	abort();
-
-	return 0;
 }

src/backend/utils/error/elog.c

@@ -1507,15 +1507,9 @@ pg_re_throw(void)
 		errfinish(0);
 	}
 
-	/* We mustn't return... */
+	/* Doesn't return ... */
 	ExceptionalCondition("pg_re_throw tried to return", "FailedAssertion",
 						 __FILE__, __LINE__);
-
-	/*
-	 * Since ExceptionalCondition isn't declared noreturn because of
-	 * TrapMacro(), we need this to keep gcc from complaining.
-	 */
-	abort();
 }
 
 

src/include/postgres.h

@@ -655,14 +655,14 @@ extern PGDLLIMPORT bool assert_enabled;
 /*
  *	TrapMacro is the same as Trap but it's intended for use in macros:
  *
- *		#define foo(x) (AssertMacro(x != 0) && bar(x))
+ *		#define foo(x) (AssertMacro(x != 0), bar(x))
  *
  *	Isn't CPP fun?
  */
 #define TrapMacro(condition, errorType) \
 	((bool) ((! assert_enabled) || ! (condition) || \
 			 (ExceptionalCondition(CppAsString(condition), (errorType), \
-								   __FILE__, __LINE__))))
+								   __FILE__, __LINE__), 0)))
 
 #ifndef USE_ASSERT_CHECKING
 #define Assert(condition)
@@ -683,8 +683,8 @@ extern PGDLLIMPORT bool assert_enabled;
 		Trap(!(condition), "BadState")
 #endif   /* USE_ASSERT_CHECKING */
 
-extern int ExceptionalCondition(const char *conditionName,
+extern void ExceptionalCondition(const char *conditionName,
 					 const char *errorType,
-					 const char *fileName, int lineNumber);
+					 const char *fileName, int lineNumber) __attribute__((noreturn));
 
 #endif   /* POSTGRES_H */