[flang-commits] [flang] [Flang][Runtime] Handle missing definitions in <cfenv> (PR #101242)

[via flang-commits]

https://github.com/serge-sans-paille created https://github.com/llvm/llvm-project/pull/101242

According to the C99 standard, <fenv.h> may not define FE_INVALID and the likes. Even if C++11 mandate them, musl and emscripten don't provide them, so handle that case.

>From 173a4435e4f4e6dd3e6fd10cfae5059c6128b1b4 Mon Sep 17 00:00:00 2001
From: serge-sans-paille <sguelton at mozilla.com>
Date: Mon, 29 Jul 2024 10:11:21 +0200
Subject: [PATCH] [Flang][Runtime] Handle missing definitions in <cfenv>

According to the C99 standard, <fenv.h> may not define FE_INVALID and
the likes. Even if C++11 mandate them, musl and emscripten don't provide
them, so handle that case.
---
 flang/runtime/edit-input.cpp | 11 +++++++++++
 flang/runtime/exceptions.cpp | 17 +++++++++++++++++
 flang/runtime/stop.cpp       | 10 ++++++++++
 3 files changed, 38 insertions(+)

diff --git a/flang/runtime/edit-input.cpp b/flang/runtime/edit-input.cpp
index 37989bbcee0ab..ec900071875e7 100644
--- a/flang/runtime/edit-input.cpp
+++ b/flang/runtime/edit-input.cpp
@@ -507,18 +507,29 @@ static RT_API_ATTRS void RaiseFPExceptions(
 #define RAISE std::feraiseexcept
 #endif
 #endif // !defined(RT_DEVICE_COMPILATION)
+
+// Some environment (e.g. emscripten, musl) don't define FE_OVERFLOW as allowed
+// by c99 (but not c++11) :-/
+#if defined(FE_OVERFLOW) || defined(RT_DEVICE_COMPILATION)
   if (flags & decimal::ConversionResultFlags::Overflow) {
     RAISE(FE_OVERFLOW);
   }
+#endif
+#if defined(FE_UNDERFLOW) || defined(RT_DEVICE_COMPILATION)
   if (flags & decimal::ConversionResultFlags::Underflow) {
     RAISE(FE_UNDERFLOW);
   }
+#endif
+#if defined(FE_INEXACT) || defined(RT_DEVICE_COMPILATION)
   if (flags & decimal::ConversionResultFlags::Inexact) {
     RAISE(FE_INEXACT);
   }
+#endif
+#if defined(FE_INVALID) || defined(RT_DEVICE_COMPILATION)
   if (flags & decimal::ConversionResultFlags::Invalid) {
     RAISE(FE_INVALID);
   }
+#endif
 #undef RAISE
 }
 
diff --git a/flang/runtime/exceptions.cpp b/flang/runtime/exceptions.cpp
index 2032ce7b12242..c714061b90405 100644
--- a/flang/runtime/exceptions.cpp
+++ b/flang/runtime/exceptions.cpp
@@ -12,9 +12,26 @@
 #include "terminator.h"
 #include <cfenv>
 
+// Some system don't define those exceptions, although they are mandated by
+// c++11 standard (e.g. musl, emscripten).
+#ifndef FE_INVALID
+#define FE_INVALID 0
+#endif
 #ifndef __FE_DENORM
 #define __FE_DENORM 0 // denorm is nonstandard
 #endif
+#ifndef FE_DIVBYZERO
+#define FE_DIVBYZERO 0
+#endif
+#ifndef FE_OVERFLOW
+#define FE_OVERFLOW 0
+#endif
+#ifndef FE_UNDERFLOW
+#define FE_UNDERFLOW 0
+#endif
+#ifndef FE_INEXACT
+#define FE_INEXACT 0
+#endif
 
 namespace Fortran::runtime {
 
diff --git a/flang/runtime/stop.cpp b/flang/runtime/stop.cpp
index 98324da1d91e1..cfb36b4084020 100644
--- a/flang/runtime/stop.cpp
+++ b/flang/runtime/stop.cpp
@@ -26,21 +26,31 @@ static void DescribeIEEESignaledExceptions() {
 #endif
   if (excepts) {
     std::fputs("IEEE arithmetic exceptions signaled:", stderr);
+#ifdef FE_DIVBYZERO
     if (excepts & FE_DIVBYZERO) {
       std::fputs(" DIVBYZERO", stderr);
     }
+#endif
+#ifdef FE_INEXACT
     if (excepts & FE_INEXACT) {
       std::fputs(" INEXACT", stderr);
     }
+#endif
+#ifdef FE_INVALID
     if (excepts & FE_INVALID) {
       std::fputs(" INVALID", stderr);
     }
+#endif
+#ifdef FE_OVERFLOW
     if (excepts & FE_OVERFLOW) {
       std::fputs(" OVERFLOW", stderr);
     }
+#endif
+#ifdef FE_UNDERFLOW
     if (excepts & FE_UNDERFLOW) {
       std::fputs(" UNDERFLOW", stderr);
     }
+#endif
     std::fputc('\n', stderr);
   }
 }