Revert "Revert "[analyzer] Make MallocChecker more robust against custom redeclarations""

This reverts commit r284340 to reapply r284335. The bot breakage was due to
an unrelated change in the polybench test suite.

llvm-svn: 284351

clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp

@@ -778,6 +778,8 @@ void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
           State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
       }
     } else if (FunI == II_kmalloc) {
+      if (CE->getNumArgs() < 1)
+        return;
       llvm::Optional<ProgramStateRef> MaybeState =
         performKernelMalloc(CE, C, State);
       if (MaybeState.hasValue())
@@ -807,6 +809,8 @@ void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
     } else if (FunI == II_strndup) {
       State = MallocUpdateRefState(C, CE, State);
     } else if (FunI == II_alloca || FunI == II_win_alloca) {
+      if (CE->getNumArgs() < 1)
+        return;
       State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State,
                            AF_Alloca);
       State = ProcessZeroAllocation(C, CE, 0, State);

clang/test/Analysis/malloc-custom.c

@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=core,unix.Malloc -Wno-incompatible-library-redeclaration -verify %s
+
+// Various tests to make the the analyzer is robust against custom
+// redeclarations of memory routines.
+//
+// You wouldn't expect to see much of this in normal code, but, for example,
+// CMake tests can generate these.
+
+// expected-no-diagnostics
+
+char alloca();
+char malloc();
+char realloc();
+char kmalloc();
+char valloc();
+char calloc();
+
+char free();
+char kfree();
+
+void testCustomArgumentlessAllocation() {
+  alloca(); // no-crash
+  malloc(); // no-crash
+  realloc(); // no-crash
+  kmalloc(); // no-crash
+  valloc(); // no-crash
+  calloc(); // no-crash
+
+  free(); // no-crash
+  kfree(); // no-crash
+}
+