Bug 1181411 - Test some expected aborts in PLDHashTable. r=glandium.

Author: nnethercote

toolkit/xre/nsSigHandlers.cpp

@@ -38,7 +38,9 @@
 #endif
 
 static char _progname[1024] = "huh?";
-static unsigned int _gdb_sleep_duration = 300;
+
+// Note: some tests manipulate this value.
+unsigned int _gdb_sleep_duration = 300;
 
 #if defined(LINUX) && defined(DEBUG) && \
       (defined(__i386) || defined(__x86_64) || defined(PPC))

xpcom/tests/gtest/TestPLDHash.cpp

@@ -10,23 +10,109 @@
 // This test mostly focuses on edge cases. But more coverage of normal
 // operations wouldn't be a bad thing.
 
+#ifdef XP_UNIX
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+// This global variable is defined in toolkit/xre/nsSigHandlers.cpp.
+extern unsigned int _gdb_sleep_duration;
+#endif
+
+// We can test that certain operations cause expected aborts by forking
+// and then checking that the child aborted in the expected way (i.e. via
+// MOZ_CRASH). We skip this for the following configurations.
+// - On Windows, because it doesn't have fork().
+// - On non-DEBUG builds, because the crashes cause the crash reporter to pop
+//   up when running this test locally, which is surprising and annoying.
+// - On ASAN builds, because ASAN alters the way a MOZ_CRASHing process
+//   terminates, which makes it harder to test if the right thing has occurred.
+void
+TestCrashyOperation(void (*aCrashyOperation)())
+{
+#if defined(XP_UNIX) && defined(DEBUG) && !defined(MOZ_ASAN)
+  // We're about to trigger a crash. When it happens don't pause to allow GDB
+  // to be attached.
+  unsigned int old_gdb_sleep_duration = _gdb_sleep_duration;
+  _gdb_sleep_duration = 0;
+
+  int pid = fork();
+  ASSERT_NE(pid, -1);
+
+  if (pid == 0) {
+    // Child: perform the crashy operation.
+    aCrashyOperation();
+    fprintf(stderr, "TestCrashyOperation: didn't crash?!\n");
+    ASSERT_TRUE(false);   // shouldn't reach here
+  }
+
+  // Parent: check that child crashed as expected.
+  int status;
+  ASSERT_NE(waitpid(pid, &status, 0), -1);
+
+  // The path taken here depends on the platform and configuration.
+  ASSERT_TRUE(WIFEXITED(status) || WTERMSIG(status));
+  if (WIFEXITED(status)) {
+    // This occurs if the ah_crap_handler() is run, i.e. we caught the crash.
+    // It returns the number of the caught signal.
+    int signum = WEXITSTATUS(status);
+    if (signum != SIGSEGV && signum != SIGBUS) {
+      fprintf(stderr, "TestCrashyOperation 'exited' failure: %d\n", signum);
+      ASSERT_TRUE(false);
+    }
+  } else if (WIFSIGNALED(status)) {
+    // This one occurs if we didn't catch the crash. The exit code is the
+    // number of the terminating signal.
+    int signum = WTERMSIG(status);
+    if (signum != SIGSEGV && signum != SIGBUS) {
+      fprintf(stderr, "TestCrashyOperation 'signaled' failure: %d\n", signum);
+      ASSERT_TRUE(false);
+    }
+  }
+
+  _gdb_sleep_duration = old_gdb_sleep_duration;
+#endif
+}
+
+void
+InitCapacityOk_InitialLengthTooBig()
+{
+  PLDHashTable t(PL_DHashGetStubOps(), sizeof(PLDHashEntryStub),
+                 PL_DHASH_MAX_INITIAL_LENGTH + 1);
+}
+
+void
+InitCapacityOk_InitialEntryStoreTooBig()
+{
+  // Try the smallest disallowed power-of-two entry store size, which is 2^32
+  // bytes (which overflows to 0). (Note that the 2^23 *length* gets converted
+  // to a 2^24 *capacity*.)
+  PLDHashTable t(PL_DHashGetStubOps(), (uint32_t)1 << 23, (uint32_t)1 << 8);
+}
+
 TEST(PLDHashTableTest, InitCapacityOk)
 {
   // Try the largest allowed capacity.  With PL_DHASH_MAX_CAPACITY==1<<26, this
   // would allocate (if we added an element) 0.5GB of entry store on 32-bit
   // platforms and 1GB on 64-bit platforms.
-  //
-  // Ideally we'd also try (a) a too-large capacity, and (b) a large capacity
-  // combined with a large entry size that when multipled overflow. But those
-  // cases would cause the test to abort immediately.
-  //
-  // Furthermore, ideally we'd also try a large-but-ok capacity that almost but
-  // doesn't quite overflow, but that would result in allocating just under 4GB
-  // of entry storage.  That's very likely to fail on 32-bit platforms, so such
-  // a test wouldn't be reliable.
-  //
-  PLDHashTable t(PL_DHashGetStubOps(), sizeof(PLDHashEntryStub),
+  PLDHashTable t1(PL_DHashGetStubOps(), sizeof(PLDHashEntryStub),
                  PL_DHASH_MAX_INITIAL_LENGTH);
+
+  // Try the largest allowed power-of-two entry store size, which is 2^31 bytes
+  // (Note that the 2^23 *length* gets converted to a 2^24 *capacity*.)
+  PLDHashTable t2(PL_DHashGetStubOps(), (uint32_t)1 << 23, (uint32_t)1 << 7);
+
+  // Try a too-large capacity (which aborts).
+  TestCrashyOperation(InitCapacityOk_InitialLengthTooBig);
+
+  // Try a large capacity combined with a large entry size that when multiplied
+  // overflow (causing abort).
+  TestCrashyOperation(InitCapacityOk_InitialEntryStoreTooBig);
+
+  // Ideally we'd also try a large-but-ok capacity that almost but doesn't
+  // quite overflow, but that would result in allocating slightly less than 4
+  // GiB of entry storage. That would be very likely to fail on 32-bit
+  // platforms, so such a test wouldn't be reliable.
 }
 
 TEST(PLDHashTableTest, LazyStorage)
@@ -141,7 +227,7 @@ TEST(PLDHashTableTest, Clear)
   ASSERT_EQ(t1.EntryCount(), 0u);
 }
 
-TEST(PLDHashTableIterator, Iterator)
+TEST(PLDHashTableTest, Iterator)
 {
   PLDHashTable t(&trivialOps, sizeof(PLDHashEntryStub));