logging: fix the behavior of XLOG_IF(FATAL, condition)

Summary:
Previously `XLOG_IF(FATAL, condition)` always crashed regardless of the
condition check.  When `XLOG_IF()` was added it did not update the checks used
to mark the statement as `[noreturn]` based on the log level.  As a result
`XLOG_IF(FATAL, ...)` always used the `[noreturn]` APIs, even though this code
can return if the condition is not true.

This splits the `XLOG()` and `XLOG_IF()` implementations so that `XLOG(FATAL)`
can still be marked as `noreturn` but `XLOG_IF(FATAL, ...)` is no `noreturn`.

Reviewed By: yfeldblum, mnv104

Differential Revision: D8817269

fbshipit-source-id: 47a493eaaac69c563cff07da0888dd423f7dc07d

folly/logging/printf.h

@@ -47,7 +47,11 @@ std::string loggingFormatPrintf(
  * Log a message to the file's default log category using a printf-style format
  * string.
  */
-#define XLOGC(level, fmt, ...) XLOGC_IF(level, true, fmt, ##__VA_ARGS__)
+#define XLOGC(level, fmt, ...)             \
+  XLOG_IMPL(                               \
+      ::folly::LogLevel::level,            \
+      ::folly::LogStreamProcessor::APPEND, \
+      ::folly::loggingFormatPrintf(fmt, ##__VA_ARGS__))
 
 /**
  * Log a message using a printf-style format string if and only if the
@@ -55,7 +59,7 @@ std::string loggingFormatPrintf(
  * is *only* evaluated if the log-level check passes.
  */
 #define XLOGC_IF(level, cond, fmt, ...)    \
-  XLOG_IMPL(                               \
+  XLOG_IF_IMPL(                            \
       ::folly::LogLevel::level,            \
       cond,                                \
       ::folly::LogStreamProcessor::APPEND, \

folly/logging/test/FatalHelper.cpp

@@ -16,12 +16,21 @@
 #include <folly/init/Init.h>
 #include <folly/logging/xlog.h>
 #include <folly/portability/Stdlib.h>
+#include <iostream>
 
 DEFINE_string(
     category,
     "",
     "Crash with a message to this category instead of the default");
 DEFINE_bool(crash, true, "Crash with a fatal log message.");
+DEFINE_bool(
+    check_debug,
+    false,
+    "Print whether this binary was built in debug mode "
+    "and then exit successfully");
+
+DEFINE_bool(fail_fatal_xlog_if, false, "Fail an XLOG_IF(FATAL) check.");
+DEFINE_bool(fail_dfatal_xlog_if, false, "Fail an XLOG_IF(DFATAL) check.");
 
 using folly::LogLevel;
 
@@ -83,6 +92,15 @@ std::string fbLogFatalCheck() {
 int main(int argc, char* argv[]) {
   auto init = folly::Init(&argc, &argv);
 
+  if (FLAGS_check_debug) {
+    std::cout << "DEBUG=" << static_cast<int>(folly::kIsDebug) << "\n";
+    return 0;
+  }
+
+  XLOG_IF(FATAL, FLAGS_fail_fatal_xlog_if) << "--fail_fatal_xlog_if specified!";
+  XLOG_IF(DFATAL, FLAGS_fail_dfatal_xlog_if)
+      << "--fail_dfatal_xlog_if specified!";
+
   // Do most of the work in a separate helper function.
   //
   // The main reason for putting this in a helper function is to ensure that

folly/logging/test/fatal_test.py

@@ -33,11 +33,21 @@ class FatalTests(unittest.TestCase):
             )
 
     def run_helper(self, *args, **kwargs):
-        """
-        Run the helper.
+        """Run the helper and verify it crashes.
+
         Check that it crashes with SIGABRT and prints nothing on stdout.
         Returns the data printed to stderr.
         """
+        returncode, out, err = self.run_helper_nochecks(*args, **kwargs)
+        self.assertEqual(returncode, -signal.SIGABRT)
+        self.assertEqual(out, b"")
+        return err
+
+    def run_helper_nochecks(self, *args, **kwargs):
+        """Run the helper.
+
+        Returns a tuple of [returncode, stdout_output, stderr_output]
+        """
         env = kwargs.pop("env", None)
         if kwargs:
             raise TypeError("unexpected keyword arguments: %r" % (list(kwargs.keys())))
@@ -48,11 +58,18 @@ class FatalTests(unittest.TestCase):
             cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, env=env
         )
         out, err = p.communicate()
-        status = p.returncode
+        return p.returncode, out, err
 
-        self.assertEqual(status, -signal.SIGABRT)
-        self.assertEqual(out, b"")
-        return err
+    def is_debug_build(self):
+        returncode, out, err = self.run_helper_nochecks("--check_debug")
+        self.assertEqual(b"", err)
+        self.assertEqual(0, returncode)
+        if out.strip() == b"DEBUG=1":
+            return True
+        elif out.strip() == b"DEBUG=0":
+            return False
+        else:
+            self.fail("unexpected output from --check_debug: {}".format(out))
 
     def get_crash_regex(self, msg=b"test program crashing!", glog=True):
         if glog:
@@ -65,7 +82,10 @@ class FatalTests(unittest.TestCase):
     def test_no_crash(self):
         # Simple sanity check that the program runs without
         # crashing when requested
-        subprocess.check_output([self.helper, "--crash=no"])
+        returncode, out, err = self.run_helper_nochecks("--crash=no")
+        self.assertEqual(0, returncode)
+        self.assertEqual(b"", out)
+        self.assertEqual(b"", err)
 
     def test_async(self):
         handler_setings = "default=stream:stream=stderr,async=true"
@@ -109,3 +129,22 @@ class FatalTests(unittest.TestCase):
             re.MULTILINE,
         )
         self.assertRegex(err, regex)
+
+    def test_fatal_xlog_if(self):
+        # Specify --crash=no to ensure that the XLOG_IF() check is actually what
+        # triggers the crash.
+        err = self.run_helper("--fail_fatal_xlog_if", "--crash=no")
+        self.assertRegex(err, self.get_crash_regex(b"--fail_fatal_xlog_if specified!"))
+
+    def test_dfatal_xlog_if(self):
+        returncode, out, err = self.run_helper_nochecks(
+            "--fail_dfatal_xlog_if", "--crash=no"
+        )
+        # The "--fail_dfatal_xlog_if" message should be logged regardless of which build
+        # type we are using.  However, in debug builds it will not trigger a crash.
+        self.assertRegex(err, self.get_crash_regex(b"--fail_dfatal_xlog_if specified!"))
+        self.assertEqual(b"", out)
+        if self.is_debug_build():
+            self.assertEqual(-signal.SIGABRT, returncode)
+        else:
+            self.assertEqual(0, returncode)

folly/logging/xlog.h

@@ -54,7 +54,11 @@
  * best if you always invoke the compiler from the root directory of your
  * project repository.
  */
-#define XLOG(level, ...) XLOG_IF(level, true, ##__VA_ARGS__)
+#define XLOG(level, ...)                   \
+  XLOG_IMPL(                               \
+      ::folly::LogLevel::level,            \
+      ::folly::LogStreamProcessor::APPEND, \
+      ##__VA_ARGS__)
 
 /**
  * Log a message if and only if the specified condition predicate evaluates
@@ -62,7 +66,7 @@
  * passes.
  */
 #define XLOG_IF(level, cond, ...)          \
-  XLOG_IMPL(                               \
+  XLOG_IF_IMPL(                            \
       ::folly::LogLevel::level,            \
       cond,                                \
       ::folly::LogStreamProcessor::APPEND, \
@@ -71,7 +75,12 @@
  * Log a message to this file's default log category, using a format string.
  */
 #define XLOGF(level, fmt, arg1, ...)       \
-  XLOGF_IF(level, true, fmt, arg1, ##__VA_ARGS__)
+  XLOG_IMPL(                               \
+      ::folly::LogLevel::level,            \
+      ::folly::LogStreamProcessor::FORMAT, \
+      fmt,                                 \
+      arg1,                                \
+      ##__VA_ARGS__)
 
 /**
  * Log a message using a format string if and only if the specified condition
@@ -79,7 +88,7 @@
  * if the log-level check passes.
  */
 #define XLOGF_IF(level, cond, fmt, arg1, ...) \
-  XLOG_IMPL(                                  \
+  XLOG_IF_IMPL(                               \
       ::folly::LogLevel::level,               \
       cond,                                   \
       ::folly::LogStreamProcessor::FORMAT,    \
@@ -153,10 +162,17 @@
 #define XLOG_FILENAME __FILE__
 #endif
 
+#define XLOG_IMPL(level, type, ...) \
+  XLOG_ACTUAL_IMPL(                 \
+      level, true, ::folly::isLogLevelFatal(level), type, ##__VA_ARGS__)
+
+#define XLOG_IF_IMPL(level, cond, type, ...) \
+  XLOG_ACTUAL_IMPL(level, cond, false, type, ##__VA_ARGS__)
+
 /**
  * Helper macro used to implement XLOG() and XLOGF()
  *
- * Beware that the level argument is evalutated twice.
+ * Beware that the level argument is evaluated twice.
  *
  * This macro is somewhat tricky:
  *
@@ -196,10 +212,9 @@
  *   initialized.  On all subsequent calls, disabled log statements can be
  *   skipped with just a single check of the LogLevel.
  */
-#define XLOG_IMPL(level, cond, type, ...)                                \
+#define XLOG_ACTUAL_IMPL(level, cond, always_fatal, type, ...)             \
   (!XLOG_IS_ON_IMPL(level) || !(cond))                                     \
-      ? ::folly::logDisabledHelper(                                      \
-            ::folly::bool_constant<::folly::isLogLevelFatal(level)>{})   \
+      ? ::folly::logDisabledHelper(::folly::bool_constant<always_fatal>{}) \
       : ::folly::LogStreamVoidify<::folly::isLogLevelFatal(level)>{} &     \
           ::folly::LogStreamProcessor(                                     \
               [] {                                                         \
@@ -218,7 +233,7 @@
               .stream()
 
 /**
- * Check if and XLOG() statement with the given log level would be enabled.
+ * Check if an XLOG() statement with the given log level would be enabled.
  *
  * The level parameter must be an unqualified LogLevel enum value.
  */