[analyzer] Split the MallocChecker into two versions - pessimistic and

optimistic.

TODO: actually implement the pessimistic version of the checker. Ex: it
needs to assume that any function that takes a pointer might free it.

The optimistic version relies on annotations to tell us which functions
can free the pointer.

llvm-svn: 150111

clang/lib/StaticAnalyzer/Checkers/Checkers.td

@@ -282,8 +282,12 @@ def ChrootChecker : Checker<"Chroot">,
   HelpText<"Check improper use of chroot">,
   DescFile<"ChrootChecker.cpp">;
 
-def MallocChecker : Checker<"Malloc">,
-  HelpText<"Check for potential memory leaks, double free, and use-after-free problems">,
+def MallocOptimistic : Checker<"MallocWithAnnotations">,
+  HelpText<"Check for memory leaks, double free, and use-after-free problems. Assumes that all user-defined functions which might free a pointer are annotated.">,
+  DescFile<"MallocChecker.cpp">;
+
+def MallocPessimistic : Checker<"Malloc">,
+  HelpText<"Check for memory leaks, double free, and use-after-free problems.">,
   DescFile<"MallocChecker.cpp">;
 
 def MallocSizeofChecker : Checker<"MallocSizeof">,

clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp

@@ -83,6 +83,16 @@ class MallocChecker : public Checker<check::DeadSymbols,
 
 public:
   MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0) {}
+
+  /// In pessimistic mode, the checker assumes that it does not know which
+  /// functions might free the memory.
+  struct ChecksFilter {
+    DefaultBool CMallocPessimistic;
+    DefaultBool CMallocOptimistic;
+  };
+
+  ChecksFilter Filter;
+
   void initIdentifierInfo(CheckerContext &C) const;
 
   void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
@@ -750,6 +760,10 @@ void MallocChecker::checkBind(SVal location, SVal val,
   }
 }
 
-void ento::registerMallocChecker(CheckerManager &mgr) {
-  mgr.registerChecker<MallocChecker>();
+#define REGISTER_CHECKER(name) \
+void ento::register##name(CheckerManager &mgr) {\
+  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
 }
+
+REGISTER_CHECKER(MallocPessimistic)
+REGISTER_CHECKER(MallocOptimistic)

clang/test/Analysis/free.c

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -analyze -analyzer-store=region -analyzer-checker=core,experimental.unix.Malloc -fblocks -verify %s
+// RUN: %clang_cc1 -analyze -analyzer-store=region -analyzer-checker=core,experimental.unix.MallocWithAnnotations -fblocks -verify %s
 void free(void *);
 
 void t1 () {

clang/test/Analysis/malloc-annotations.c

@@ -0,0 +1,263 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=core,experimental.deadcode.UnreachableCode,experimental.core.CastSize,experimental.unix.MallocWithAnnotations -analyzer-store=region -verify %s
+typedef __typeof(sizeof(int)) size_t;
+void *malloc(size_t);
+void free(void *);
+void *realloc(void *ptr, size_t size);
+void *calloc(size_t nmemb, size_t size);
+void __attribute((ownership_returns(malloc))) *my_malloc(size_t);
+void __attribute((ownership_takes(malloc, 1))) my_free(void *);
+void __attribute((ownership_returns(malloc, 1))) *my_malloc2(size_t);
+void __attribute((ownership_holds(malloc, 1))) my_hold(void *);
+
+// Duplicate attributes are silly, but not an error.
+// Duplicate attribute has no extra effect.
+// If two are of different kinds, that is an error and reported as such.
+void __attribute((ownership_holds(malloc, 1)))
+__attribute((ownership_holds(malloc, 1)))
+__attribute((ownership_holds(malloc, 3))) my_hold2(void *, void *, void *);
+void *my_malloc3(size_t);
+void *myglobalpointer;
+struct stuff {
+  void *somefield;
+};
+struct stuff myglobalstuff;
+
+void f1() {
+  int *p = malloc(12);
+  return; // expected-warning{{Allocated memory never released. Potential memory leak.}}
+}
+
+void f2() {
+  int *p = malloc(12);
+  free(p);
+  free(p); // expected-warning{{Try to free a memory block that has been released}}
+}
+
+void f2_realloc_0() {
+  int *p = malloc(12);
+  realloc(p,0);
+  realloc(p,0); // expected-warning{{Try to free a memory block that has been released}}
+}
+
+void f2_realloc_1() {
+  int *p = malloc(12);
+  int *q = realloc(p,0); // no-warning
+}
+
+// ownership attributes tests
+void naf1() {
+  int *p = my_malloc3(12);
+  return; // no-warning
+}
+
+void n2af1() {
+  int *p = my_malloc2(12);
+  return; // expected-warning{{Allocated memory never released. Potential memory leak.}}
+}
+
+void af1() {
+  int *p = my_malloc(12);
+  return; // expected-warning{{Allocated memory never released. Potential memory leak.}}
+}
+
+void af1_b() {
+  int *p = my_malloc(12); // expected-warning{{Allocated memory never released. Potential memory leak.}}
+}
+
+void af1_c() {
+  myglobalpointer = my_malloc(12); // no-warning
+}
+
+void af1_d() {
+  struct stuff mystuff;
+  mystuff.somefield = my_malloc(12); // expected-warning{{Allocated memory never released. Potential memory leak.}}
+}
+
+// Test that we can pass out allocated memory via pointer-to-pointer.
+void af1_e(void **pp) {
+  *pp = my_malloc(42); // no-warning
+}
+
+void af1_f(struct stuff *somestuff) {
+  somestuff->somefield = my_malloc(12); // no-warning
+}
+
+// Allocating memory for a field via multiple indirections to our arguments is OK.
+void af1_g(struct stuff **pps) {
+  *pps = my_malloc(sizeof(struct stuff)); // no-warning
+  (*pps)->somefield = my_malloc(42); // no-warning
+}
+
+void af2() {
+  int *p = my_malloc(12);
+  my_free(p);
+  free(p); // expected-warning{{Try to free a memory block that has been released}}
+}
+
+void af2b() {
+  int *p = my_malloc(12);
+  free(p);
+  my_free(p); // expected-warning{{Try to free a memory block that has been released}}
+}
+
+void af2c() {
+  int *p = my_malloc(12);
+  free(p);
+  my_hold(p); // expected-warning{{Try to free a memory block that has been released}}
+}
+
+void af2d() {
+  int *p = my_malloc(12);
+  free(p);
+  my_hold2(0, 0, p); // expected-warning{{Try to free a memory block that has been released}}
+}
+
+// No leak if malloc returns null.
+void af2e() {
+  int *p = my_malloc(12);
+  if (!p)
+    return; // no-warning
+  free(p); // no-warning
+}
+
+// This case would inflict a double-free elsewhere.
+// However, this case is considered an analyzer bug since it causes false-positives.
+void af3() {
+  int *p = my_malloc(12);
+  my_hold(p);
+  free(p); // no-warning
+}
+
+// This case would inflict a double-free elsewhere.
+// However, this case is considered an analyzer bug since it causes false-positives.
+int * af4() {
+  int *p = my_malloc(12);
+  my_free(p);
+  return p; // no-warning
+}
+
+// This case is (possibly) ok, be conservative
+int * af5() {
+  int *p = my_malloc(12);
+  my_hold(p);
+  return p; // no-warning
+}
+
+
+
+// This case tests that storing malloc'ed memory to a static variable which is
+// then returned is not leaked.  In the absence of known contracts for functions
+// or inter-procedural analysis, this is a conservative answer.
+int *f3() {
+  static int *p = 0;
+  p = malloc(12);
+  return p; // no-warning
+}
+
+// This case tests that storing malloc'ed memory to a static global variable
+// which is then returned is not leaked.  In the absence of known contracts for
+// functions or inter-procedural analysis, this is a conservative answer.
+static int *p_f4 = 0;
+int *f4() {
+  p_f4 = malloc(12);
+  return p_f4; // no-warning
+}
+
+int *f5() {
+  int *q = malloc(12);
+  q = realloc(q, 20);
+  return q; // no-warning
+}
+
+void f6() {
+  int *p = malloc(12);
+  if (!p)
+    return; // no-warning
+  else
+    free(p);
+}
+
+void f6_realloc() {
+  int *p = malloc(12);
+  if (!p)
+    return; // no-warning
+  else
+    realloc(p,0);
+}
+
+
+char *doit2();
+void pr6069() {
+  char *buf = doit2();
+  free(buf);
+}
+
+void pr6293() {
+  free(0);
+}
+
+void f7() {
+  char *x = (char*) malloc(4);
+  free(x);
+  x[0] = 'a'; // expected-warning{{Use dynamically allocated memory after it is freed.}}
+}
+
+void f7_realloc() {
+  char *x = (char*) malloc(4);
+  realloc(x,0);
+  x[0] = 'a'; // expected-warning{{Use dynamically allocated memory after it is freed.}}
+}
+
+void PR6123() {
+  int *x = malloc(11); // expected-warning{{Cast a region whose size is not a multiple of the destination type size.}}
+}
+
+void PR7217() {
+  int *buf = malloc(2); // expected-warning{{Cast a region whose size is not a multiple of the destination type size.}}
+  buf[1] = 'c'; // not crash
+}
+
+void mallocCastToVoid() {
+  void *p = malloc(2);
+  const void *cp = p; // not crash
+  free(p);
+}
+
+void mallocCastToFP() {
+  void *p = malloc(2);
+  void (*fp)() = p; // not crash
+  free(p);
+}
+
+// This tests that malloc() buffers are undefined by default
+char mallocGarbage () {
+  char *buf = malloc(2);
+  char result = buf[1]; // expected-warning{{undefined}}
+  free(buf);
+  return result;
+}
+
+// This tests that calloc() buffers need to be freed
+void callocNoFree () {
+  char *buf = calloc(2,2);
+  return; // expected-warning{{never released}}
+}
+
+// These test that calloc() buffers are zeroed by default
+char callocZeroesGood () {
+  char *buf = calloc(2,2);
+  char result = buf[3]; // no-warning
+  if (buf[1] == 0) {
+    free(buf);
+  }
+  return result; // no-warning
+}
+
+char callocZeroesBad () {
+  char *buf = calloc(2,2);
+  char result = buf[3]; // no-warning
+  if (buf[1] != 0) {
+    free(buf); // expected-warning{{never executed}}
+  }
+  return result; // expected-warning{{never released}}
+}