Make the build work with -Wformat=2 (#2088)

* Make the build work with -Wformat=2

The -Wformat=2 macro requires every format string either be a string
literal, or a parameter that was tagged with the format attribute. The
upshot is that it expects every printf function to be marked, or you get
warnings like this:

    src/console_reporter.cc:104:23: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
      104 |   out << FormatString(fmt, args);
          |                       ^~~

Marking such things is generally worthwhile since it turns on
error-checking within the library, so fill in the missing ones.

Tested with:

    bazelisk build --copt=-Werror --copt=-Wformat=2 :all

* Add -Wformat=2 to catch regressions

Author: davidben

BUILD.bazel

@@ -12,6 +12,7 @@ COPTS = [
     "-Wshadow",
     #    "-Wshorten-64-to-32",
     "-Wfloat-equal",
+    "-Wformat=2",
     "-fstrict-aliasing",
     ## assert() are used a lot in tests upstream, which may be optimised out leading to
     ## unused-variable warning.

CMakeLists.txt

@@ -197,6 +197,7 @@ else()
   add_cxx_compiler_flag(-Wfloat-equal)
   add_cxx_compiler_flag(-Wold-style-cast)
   add_cxx_compiler_flag(-Wconversion)
+  add_cxx_compiler_flag(-Wformat=2)
   if(BENCHMARK_ENABLE_WERROR)
       add_cxx_compiler_flag(-Werror)
   endif()

src/colorprint.h

@@ -5,6 +5,8 @@
 #include <iostream>
 #include <string>
 
+#include "internal_macros.h"
+
 namespace benchmark {
 enum LogColor {
   COLOR_DEFAULT,
@@ -17,16 +19,6 @@ enum LogColor {
   COLOR_WHITE
 };
 
-#if defined(__GNUC__) || defined(__clang__)
-#define PRINTF_FORMAT_STRING_FUNC(format_arg, first_idx) \
-  __attribute__((format(printf, format_arg, first_idx)))
-#elif defined(__MINGW32__)
-#define PRINTF_FORMAT_STRING_FUNC(format_arg, first_idx) \
-  __attribute__((format(__MINGW_PRINTF_FORMAT, format_arg, first_idx)))
-#else
-#define PRINTF_FORMAT_STRING_FUNC(format_arg, first_idx)
-#endif
-
 PRINTF_FORMAT_STRING_FUNC(1, 0)
 std::string FormatString(const char* msg, va_list args);
 PRINTF_FORMAT_STRING_FUNC(1, 2) std::string FormatString(const char* msg, ...);

src/console_reporter.cc

@@ -97,6 +97,7 @@ void ConsoleReporter::ReportRuns(const std::vector<Run>& reports) {
   }
 }
 
+PRINTF_FORMAT_STRING_FUNC(3, 4)
 static void IgnoreColorPrint(std::ostream& out, LogColor /*unused*/,
                              const char* fmt, ...) {
   va_list args;

src/internal_macros.h

@@ -106,6 +106,16 @@
   #define BENCHMARK_MAYBE_UNUSED
 #endif
 
+#if defined(__GNUC__) || defined(__clang__)
+#define PRINTF_FORMAT_STRING_FUNC(format_arg, first_idx) \
+  __attribute__((format(printf, format_arg, first_idx)))
+#elif defined(__MINGW32__)
+#define PRINTF_FORMAT_STRING_FUNC(format_arg, first_idx) \
+  __attribute__((format(__MINGW_PRINTF_FORMAT, format_arg, first_idx)))
+#else
+#define PRINTF_FORMAT_STRING_FUNC(format_arg, first_idx)
+#endif
+
 // clang-format on
 
 #endif  // BENCHMARK_INTERNAL_MACROS_H_

src/string_util.cc

@@ -112,6 +112,7 @@ std::string ToBinaryStringFullySpecified(double value, int precision,
   return mantissa + ExponentToPrefix(exponent, one_k == Counter::kIs1024);
 }
 
+PRINTF_FORMAT_STRING_FUNC(1, 0)
 std::string StrFormatImp(const char* msg, va_list args) {
   // we might need a second shot at this, so pre-emptivly make a copy
   va_list args_cp;