Fix for warnings from Intel compiler on macOS.

[jeremygibbs]

On macOS using the latest Intel compilers, the code emits these warnings:

hedley.h(1261): warning #161: unrecognized #pragma
  HEDLEY_DIAGNOSTIC_PUSH
  ^

hedley.h(1287): warning #161: unrecognized #pragma
  HEDLEY_DIAGNOSTIC_POP

This seems to be because the Intel cxx compiler, icpc, defines the clang macro. I added an additional check on the relevant part of the code to make sure an Intel compiler is not being used. I wasn't sure if there was a better way you prefer, but the warnings go away with this small change and did not seem to affect compilation with a clang compiler.

[nemequ]

Do you still have access to icpc on macOS? I've added several icpc on Linux jobs to CI (in the dev branch), which work well, but I don't see a way to install icc/icpc classic on macOS during CI. Honestly, I don't even see a way to do it if I had a macOS machine (which I don't) without spending a ton of money.

I suspect that they've fixed this issue, though I've only been able to test back to version 2021.1.1, which I believe is the first version that was part of oneAPI (much easier to install in CI than the non-oneAPI verison, which I don't think is available for download anymore). If you can still reproduce this I'd love to fix it… instead of adding an exception for Intel, though, a better solution might be to reorder the Intel check to before the clang one:

diff --git a/hedley.h b/hedley.h
index ffb55f5..f92fd0e 100644
--- a/hedley.h
+++ b/hedley.h
@@ -753,12 +753,12 @@
 #if defined(HEDLEY_DIAGNOSTIC_POP)
 #  undef HEDLEY_DIAGNOSTIC_POP
 #endif
-#if defined(__clang__)
-#  define HEDLEY_DIAGNOSTIC_PUSH _Pragma("clang diagnostic push")
-#  define HEDLEY_DIAGNOSTIC_POP _Pragma("clang diagnostic pop")
-#elif HEDLEY_INTEL_VERSION_CHECK(13,0,0)
+#if HEDLEY_INTEL_VERSION_CHECK(13,0,0)
 #  define HEDLEY_DIAGNOSTIC_PUSH _Pragma("warning(push)")
 #  define HEDLEY_DIAGNOSTIC_POP _Pragma("warning(pop)")
+#elif defined(__clang__)
+#  define HEDLEY_DIAGNOSTIC_PUSH _Pragma("clang diagnostic push")
+#  define HEDLEY_DIAGNOSTIC_POP _Pragma("clang diagnostic pop")
 #elif HEDLEY_GCC_VERSION_CHECK(4,6,0)
 #  define HEDLEY_DIAGNOSTIC_PUSH _Pragma("GCC diagnostic push")
 #  define HEDLEY_DIAGNOSTIC_POP _Pragma("GCC diagnostic pop")

But I'd really like to be able to do a more complete test to make sure there are no similar issues for other macros.

FWIW, I've also added icx/icpx jobs (the new versions of icc/icpc which are based on clang), and they work well.