From f310332a6ba0427e38582673f4d3fbe4b3d9eb5c Mon Sep 17 00:00:00 2001
From: sebres <sebres@users.sourceforge.net>
Date: Tue, 25 Jun 2019 07:36:28 +0000
Subject: use __builtin_fpclassify for mingw x86 (tested up to gcc 8.1, it
 seems to have a bug in fpclassify, so [fpclassify 1e-314], x86 => normal, x64
 => subnormal)

---
 generic/tclBasic.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/generic/tclBasic.c b/generic/tclBasic.c
index a23bfc1..ea96108 100644
--- a/generic/tclBasic.c
+++ b/generic/tclBasic.c
@@ -8340,7 +8340,13 @@ ClassifyDouble(
     double d)
 {
 #ifdef fpclassify
+/* MINGW x86 (tested up to gcc 8.1) seems to have a bug in fpclassify,
+ * [fpclassify 1e-314], x86 => normal, x64 => subnormal */
+#  if defined(__MINGW32__) && defined(_X86_)
+    return __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL, FP_SUBNORMAL, FP_ZERO, d);
+#  else
     return fpclassify(d);
+#  endif
 #else /* !fpclassify */
 #define FP_ZERO 0
 #define FP_NORMAL 1
-- 
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