[StaticAnalyzer] Fix false positives for unreachable code in macros.

Example:

#define MACRO(C)   if (C) { static int x; .. }
void foo() {
	MACRO(0);
}

Differential Revision: https://reviews.llvm.org/D36141

llvm-svn: 309799

clang/lib/StaticAnalyzer/Checkers/UnreachableCodeChecker.cpp

@@ -112,7 +112,7 @@ void UnreachableCodeChecker::checkEndAnalysis(ExplodedGraph &G,
       continue;
 
     // Check for false positives
-    if (CB->size() > 0 && isInvalidPath(CB, *PM))
+    if (isInvalidPath(CB, *PM))
       continue;
 
     // It is good practice to always have a "default" label in a "switch", even

clang/test/Analysis/unreachable-code-path.c

@@ -213,3 +213,13 @@ void macro(void) {
   RETURN(1); // no-warning
 }
 
+// Avoid FP when macro argument is known
+void writeSomething(int *x);
+#define MACRO(C)        \
+  if (!C) {             \
+    static int x;       \
+    writeSomething(&x); \
+  }
+void macro2(void) {
+  MACRO(1);
+}