Bug 1791481 - Avoid tail-call optimization of call to GetAndCheckStackTrace. r=mstange

While here, change the gtest to display how many tests passed.

Differential Revision: https://phabricator.services.mozilla.com/D157888

mozglue/baseprofiler/lul/LulMain.cpp

@@ -1560,7 +1560,7 @@ static __attribute__((noinline)) unsigned long __getpc(void) {
 // This function must not be inlined into its callers.  Doing so will
 // cause the expected-vs-actual backtrace consistency checking to
 // fail.  Prints summary results to |aLUL|'s logging sink and also
-// returns a boolean indicating whether or not the test passed.
+// returns a boolean indicating whether or not the test failed.
 static __attribute__((noinline)) bool GetAndCheckStackTrace(
     LUL* aLUL, const char* dstring) {
   // Get hold of the current unwind-start registers.
@@ -1790,7 +1790,7 @@ static __attribute__((noinline)) bool GetAndCheckStackTrace(
   buf[sizeof(buf) - 1] = 0;
   aLUL->mLog(buf);
 
-  return passed;
+  return !passed;
 }
 
 // Macro magic to create a set of 8 mutually recursive functions with
@@ -1819,7 +1819,8 @@ static __attribute__((noinline)) bool GetAndCheckStackTrace(
     if (*strP == '\0') {                                                      \
       /* We've come to the end of the director string. */                     \
       /* Take a stack snapshot. */                                            \
-      return GetAndCheckStackTrace(aLUL, strPorig);                           \
+      /* We purposefully use a negation to avoid tail-call optimization */    \
+      return !GetAndCheckStackTrace(aLUL, strPorig);                          \
     } else {                                                                  \
       /* Recurse onwards.  This is a bit subtle.  The obvious */              \
       /* thing to do here is call onwards directly, from within the */        \

tools/profiler/lul/LulMain.cpp

@@ -1681,7 +1681,7 @@ static __attribute__((noinline)) unsigned long __getpc(void) {
 // This function must not be inlined into its callers.  Doing so will
 // cause the expected-vs-actual backtrace consistency checking to
 // fail.  Prints summary results to |aLUL|'s logging sink and also
-// returns a boolean indicating whether or not the test passed.
+// returns a boolean indicating whether or not the test failed.
 static __attribute__((noinline)) bool GetAndCheckStackTrace(
     LUL* aLUL, const char* dstring) {
   // Get hold of the current unwind-start registers.
@@ -1911,7 +1911,7 @@ static __attribute__((noinline)) bool GetAndCheckStackTrace(
   buf[sizeof(buf) - 1] = 0;
   aLUL->mLog(buf);
 
-  return passed;
+  return !passed;
 }
 
 // Macro magic to create a set of 8 mutually recursive functions with
@@ -1940,7 +1940,8 @@ static __attribute__((noinline)) bool GetAndCheckStackTrace(
     if (*strP == '\0') {                                                      \
       /* We've come to the end of the director string. */                     \
       /* Take a stack snapshot. */                                            \
-      return GetAndCheckStackTrace(aLUL, strPorig);                           \
+      /* We purposefully use a negation to avoid tail-call optimization */    \
+      return !GetAndCheckStackTrace(aLUL, strPorig);                          \
     } else {                                                                  \
       /* Recurse onwards.  This is a bit subtle.  The obvious */              \
       /* thing to do here is call onwards directly, from within the */        \

tools/profiler/tests/gtest/LulTest.cpp

@@ -45,7 +45,7 @@ TEST(LulIntegration, unwind_consistency)
   int nTests = 0, nTestsPassed = 0;
   RunLulUnitTests(&nTests, &nTestsPassed, lul);
   EXPECT_TRUE(nTests == 6) << "Unexpected number of tests";
-  EXPECT_TRUE(nTestsPassed == nTests) << "Not all tests passed";
+  EXPECT_EQ(nTestsPassed, nTests) << "Not all tests passed";
 
   delete lul;
 }