'-Werror=double-promotion' compilation warnings when including gtest.h

[dotanbrk]

Hi all.

I forked the gtest repository and compiled my test, using strict gcc compilation flags,
and there are compilation warnings/error when the test includes gtest headers.

Compiler: 9.4.0-1ubuntu1~20.04.1

In file included from /opt/third_party/googletest/googletest/include/gtest/gtest-matchers.h:49,
from /opt/third_party/googletest/googletest/include/gtest/internal/gtest-death-test-internal.h:47,
from /opt/third_party/googletest/googletest/include/gtest/gtest-death-test.h:43,
from /opt/third_party/googletest/googletest/include/gtest/gtest.h:64,
from /opt/third_party/googletest/googletest/src/gtest_main.cc:32:
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h: In instantiation of ‘int testing::internal::AppropriateResolution(FloatType) [with FloatType = float]’:
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:581:40: required from here
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:535:13: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
535 | if (val >= 100000.0) { // 100,000 to 999,999
| ~~~~^~~~~~~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:537:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
537 | } else if (val >= 10000.0) {
| ~~~~^~~~~~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:539:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
539 | } else if (val >= 1000.0) {
| ~~~~^~~~~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:541:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
541 | } else if (val >= 100.0) {
| ~~~~^~~~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:543:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
543 | } else if (val >= 10.0) {
| ~~~~^~~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:545:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
545 | } else if (val >= 1.0) {
| ~~~~^~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:547:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
547 | } else if (val >= 0.1) {
| ~~~~^~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:549:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
549 | } else if (val >= 0.01) {
| ~~~~^~~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:551:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
551 | } else if (val >= 0.001) {
| ~~~~^~~~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:553:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
553 | } else if (val >= 0.0001) {
| ~~~~^~~~~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:556:67: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
556 | if (static_cast(static_cast<int32_t>(val * mulfor6 + 0.5)) /
| ~~~~~~~~~~~~~~^~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:560:18: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
560 | } else if (val < 1e10) {
| ~~~~^~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:562:13: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
562 | if (val >= 1e9) { // 1,000,000,000 to 9,999,999,999
| ~~~~^~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:564:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
564 | } else if (val >= 1e8) { // 100,000,000 to 999,999,999
| ~~~~^~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:566:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
566 | } else if (val >= 1e7) { // 10,000,000 to 99,999,999
| ~~~~^~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:568:20: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
568 | } else if (val >= 1e6) { // 1,000,000 to 9,999,999
| ~~~~^~~~~~
/opt/third_party/googletest/googletest/include/gtest/gtest-printers.h:571:67: error: implicit conversion from ‘float’ to ‘double’ to match other operand of binary expression [-Werror=double-promotion]
571 | if (static_cast(static_cast<int32_t>(val / divfor6 + 0.5)) *

I wander, did you ever notice those errors?

Thanks
Dotan

[dotanbrk]

The following patch solved the compilation warning, but i don't know if this the correct fix:

diff --git a/googletest/include/gtest/gtest-printers.h b/googletest/include/gtest/gtest-printers.h
index d1766e64..c22d57d9 100644
--- a/googletest/include/gtest/gtest-printers.h
+++ b/googletest/include/gtest/gtest-printers.h
@@ -532,43 +532,43 @@ int AppropriateResolution(FloatType val) {
 
   if (val < 1000000) {
     FloatType mulfor6 = 1e10;
-    if (val >= 100000.0) {  // 100,000 to 999,999
+    if ((double)val >= 100000.0) {  // 100,000 to 999,999
       mulfor6 = 1.0;
-    } else if (val >= 10000.0) {
+    } else if ((double)val >= 10000.0) {
       mulfor6 = 1e1;
-    } else if (val >= 1000.0) {
+    } else if ((double)val >= 1000.0) {
       mulfor6 = 1e2;
-    } else if (val >= 100.0) {
+    } else if ((double)val >= 100.0) {
       mulfor6 = 1e3;
-    } else if (val >= 10.0) {
+    } else if ((double)val >= 10.0) {
       mulfor6 = 1e4;
-    } else if (val >= 1.0) {
+    } else if ((double)val >= 1.0) {
       mulfor6 = 1e5;
-    } else if (val >= 0.1) {
+    } else if ((double)val >= 0.1) {
       mulfor6 = 1e6;
-    } else if (val >= 0.01) {
+    } else if ((double)val >= 0.01) {
       mulfor6 = 1e7;
-    } else if (val >= 0.001) {
+    } else if ((double)val >= 0.001) {
       mulfor6 = 1e8;
-    } else if (val >= 0.0001) {
+    } else if ((double)val >= 0.0001) {
       mulfor6 = 1e9;
     }
-    if (static_cast<FloatType>(static_cast<int32_t>(val * mulfor6 + 0.5)) /
+    if (static_cast<FloatType>(static_cast<int32_t>((double)val * (double)mulfor6 + 0.5)) /
             mulfor6 ==
         val)
       return 6;
-  } else if (val < 1e10) {
+  } else if ((double)val < 1e10) {
     FloatType divfor6 = 1.0;
-    if (val >= 1e9) {  // 1,000,000,000 to 9,999,999,999
+    if ((double)val >= 1e9) {  // 1,000,000,000 to 9,999,999,999
       divfor6 = 10000;
-    } else if (val >= 1e8) {  // 100,000,000 to 999,999,999
+    } else if ((double)val >= 1e8) {  // 100,000,000 to 999,999,999
       divfor6 = 1000;
-    } else if (val >= 1e7) {  // 10,000,000 to 99,999,999
+    } else if ((double)val >= 1e7) {  // 10,000,000 to 99,999,999
       divfor6 = 100;
-    } else if (val >= 1e6) {  // 1,000,000 to 9,999,999
+    } else if ((double)val >= 1e6) {  // 1,000,000 to 9,999,999
       divfor6 = 10;
     }
-    if (static_cast<FloatType>(static_cast<int32_t>(val / divfor6 + 0.5)) *
+    if (static_cast<FloatType>(static_cast<int32_t>((double)val / (double)divfor6 + 0.5)) *
             divfor6 ==
         val)
       return 6;