[flang][MSVC] Fix building with `/permissive-` flag

[MehdiChinoune]

Summary

CLOCK_REALTIME is POSIX defined and never available with MSVC, even without /permissive-.
The difference is that the template is never instantiated and the compiler ignores the undefined identifier.

[Meinersbur]

Patch summary missing. What is failing with /permissive-?

[MehdiChinoune]

In D125262#3504589, @Meinersbur wrote:

Patch summary missing. What is failing with /permissive-?

CLOCKID is not defined

[MehdiChinoune]

This is the error message:

[6795/8382] Building CXX object tools\flang\runtime\CMakeFiles\obj.FortranRuntime.dir\time-intrinsic.cpp.obj
FAILED: tools/flang/runtime/CMakeFiles/obj.FortranRuntime.dir/time-intrinsic.cpp.obj
sccache C:\BuildTools\VC\Tools\MSVC\14.29.30133\bin\Hostx64\x64\cl.exe  /nologo /TP -DBUILD_EXAMPLES -DFLANG_LITTLE_ENDIAN=1 -DGTEST_HAS_RTTI=0 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools\flang\runtime -IC:\ws\w3\llvm-project\premerge-checks\flang\runtime -IC:\ws\w3\llvm-project\premerge-checks\flang\include -Itools\flang\include -Iinclude -IC:\ws\w3\llvm-project\premerge-checks\llvm\include -IC:\ws\w3\llvm-project\premerge-checks\llvm\..\mlir\include -Itools\mlir\include -Itools\clang\include -IC:\ws\w3\llvm-project\premerge-checks\llvm\..\clang\include /DWIN32 /D_WINDOWS   /Zc:inline /Zc:__cplusplus /Zc:strictStrings /Oi /Zc:rvalueCast /bigobj /permissive- /W4 -wd4141 -wd4146 -wd4244 -wd4267 -wd4291 -wd4351 -wd4456 -wd4457 -wd4458 -wd4459 -wd4503 -wd4624 -wd4722 -wd4100 -wd4127 -wd4512 -wd4505 -wd4610 -wd4510 -wd4702 -wd4245 -wd4706 -wd4310 -wd4701 -wd4703 -wd4389 -wd4611 -wd4805 -wd4204 -wd4577 -wd4091 -wd4592 -wd4319 -wd4709 -wd4324 -w14062 -we4238 /Gw /MD /O2 /Ob2 -UNDEBUG -std:c++17  /EHs-c- /GR- /showIncludes /Fotools\flang\runtime\CMakeFiles\obj.FortranRuntime.dir\time-intrinsic.cpp.obj /Fdtools\flang\runtime\CMakeFiles\obj.FortranRuntime.dir\ /FS -c C:\ws\w3\llvm-project\premerge-checks\flang\runtime\time-intrinsic.cpp
C:\ws\w3\llvm-project\premerge-checks\flang\runtime\time-intrinsic.cpp(77): error C2065: 'CLOCK_REALTIME': undeclared identifier
C:\ws\w3\llvm-project\premerge-checks\flang\runtime\time-intrinsic.cpp(77): error C3861: 'CLOCK_REALTIME': identifier not found
C:\ws\w3\llvm-project\premerge-checks\flang\runtime\time-intrinsic.cpp(146): error C2065: 'CLOCK_REALTIME': undeclared identifier
C:\ws\w3\llvm-project\premerge-checks\flang\runtime\time-intrinsic.cpp(146): error C3861: 'CLOCK_REALTIME': identifier not found

https://buildkite.com/llvm-project/premerge-checks/builds/92047#ae63959e-de4c-4cf0-a663-eeab39a06ce8/410-7338

[Meinersbur]

Please add a summary where you mention that CLOCK_REALTIME is POSIX defined and never available with msvc, even without /permissive-. The difference is that the template is never instantiated and the compiler ignores the undefined identifier. Also add a comment that without CLOCKID defined (e.g. Windows), it will fallback to the other implementation.

Interestingly, the same problem was solved differently for GetDateAndTime without the template stuff.

[MehdiChinoune]

In D125262#3512790, @Meinersbur wrote:

Please add a summary where you mention that CLOCK_REALTIME is POSIX defined and never available with msvc, even without /permissive-. The difference is that the template is never instantiated and the compiler ignores the undefined identifier.

done, I have copied your phrases.

Also add a comment that without CLOCKID defined (e.g. Windows), it will fallback to the other implementation.

It is already mentioned in the source file (line-65 and line-95)

[Meinersbur]

LGTM

[MehdiChinoune]

In D125262#3525059, @Meinersbur wrote:

LGTM

Could you push it for me, Please.

[MehdiChinoune]

Thanks.

flang/runtime/time-intrinsic.cpp

 }
 
 #if defined CLOCK_PROCESS_CPUTIME_ID
 #define CLOCKID CLOCK_PROCESS_CPUTIME_ID
 #elif defined CLOCK_THREAD_CPUTIME_ID
 #define CLOCKID CLOCK_THREAD_CPUTIME_ID
 #elif defined CLOCK_MONOTONIC
 #define CLOCKID CLOCK_MONOTONIC
-#else
+#elif defined CLOCK_REALTIME
 #define CLOCKID CLOCK_REALTIME
+#else
+#undef CLOCKID
 #endif
 
+#ifdef CLOCKID
 // POSIX implementation using clock_gettime. This is only enabled where
 // clock_gettime is available.
 template <typename T = int, typename U = struct timespec>
 double GetCpuTime(preferred_implementation,
     // We need some dummy parameters to pass to decltype(clock_gettime).
     T ClockId = 0, U *Timespec = nullptr,
     decltype(clock_gettime(ClockId, Timespec)) *Enabled = nullptr) {
   struct timespec tspec;
   if (clock_gettime(CLOCKID, &tspec) == 0) {
     return tspec.tv_nsec * 1.0e-9 + tspec.tv_sec;
   }
   // Return some negative value to represent failure.
   return -1.0;
 }
+#endif
 
 using count_t = std::int64_t;
 using unsigned_count_t = std::uint64_t;
 
 // Computes HUGE(INT(0,kind)) as an unsigned integer value.
 static constexpr inline unsigned_count_t GetHUGE(int kind) {
   if (kind > 8) {
     kind = 8;

 // result is in nanoseconds, which is converted as necessary to
 //  - deciseconds for kind 1
 //  - milliseconds for kinds 2, 4
 //  - nanoseconds for kinds 8, 16
 constexpr unsigned_count_t DS_PER_SEC{10u};
 constexpr unsigned_count_t MS_PER_SEC{1'000u};
 constexpr unsigned_count_t NS_PER_SEC{1'000'000'000u};
 
+#ifdef CLOCKID
 template <typename T = int, typename U = struct timespec>
 count_t GetSystemClockCount(int kind, preferred_implementation,
     // We need some dummy parameters to pass to decltype(clock_gettime).
     T ClockId = 0, U *Timespec = nullptr,
     decltype(clock_gettime(ClockId, Timespec)) *Enabled = nullptr) {
   struct timespec tspec;
   const unsigned_count_t huge{GetHUGE(kind)};
   if (clock_gettime(CLOCKID, &tspec) != 0) {
     return -huge; // failure
   }
   unsigned_count_t sec{static_cast<unsigned_count_t>(tspec.tv_sec)};
   unsigned_count_t nsec{static_cast<unsigned_count_t>(tspec.tv_nsec)};
   if (kind >= 8) {
     return (sec * NS_PER_SEC + nsec) % (huge + 1);
   } else if (kind >= 2) {
     return (sec * MS_PER_SEC + (nsec / (NS_PER_SEC / MS_PER_SEC))) % (huge + 1);
   } else { // kind == 1
     return (sec * DS_PER_SEC + (nsec / (NS_PER_SEC / DS_PER_SEC))) % (huge + 1);
   }
 }
+#endif
 
 template <typename T = int, typename U = struct timespec>
 count_t GetSystemClockCountRate(int kind, preferred_implementation,
     // We need some dummy parameters to pass to decltype(clock_gettime).
     T ClockId = 0, U *Timespec = nullptr,
     decltype(clock_gettime(ClockId, Timespec)) *Enabled = nullptr) {
   return kind >= 8 ? NS_PER_SEC : kind >= 2 ? MS_PER_SEC : DS_PER_SEC;
 }