From e0e56b0da80406a01d8c3e733c96b4bdfb7409ac Mon Sep 17 00:00:00 2001
From: Dmitry Volyntsev <xeioex@nginx.com>
Date: Tue, 5 Jul 2022 22:58:12 -0700
Subject: [PATCH] Ensuring that double type is always evaluated at standard
 precision.

Previously, GCC on x86 uses extended precision for intermediate
calculations by default.  This might conflict with njs_diyfp_t because
GCC is not always rounds back the intermediate values to standard
precision.

The fix is to explicitly tell to a compiler to do so.

This closes #507 issue on Github.
---
 auto/types | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/auto/types b/auto/types
index 7bb9c16a..6e1c2c61 100644
--- a/auto/types
+++ b/auto/types
@@ -118,3 +118,57 @@ njs_feature_test="#include <time.h>
                       return 0;
                   }"
 . auto/feature
+
+
+# Ensuring that double type is always evaluated at standard
+# precision required by njs_diyfp_t
+
+
+case $NJS_CC_NAME in
+
+    gcc)
+        NJS_CFLAGS="$NJS_CFLAGS -fexcess-precision=standard"
+    ;;
+
+    clang)
+
+        njs_found=no
+
+        njs_feature="flag -ffp-eval-method=double"
+        njs_feature_name=NJS_HAVE_FP_EVAL_METHOD
+        njs_feature_run=no
+        njs_feature_incs="-ffp-eval-method=double"
+        njs_feature_libs=
+        njs_feature_test="int main(void) {
+                             return 0;
+                         }"
+
+        . auto/feature
+
+        if [ $njs_found = yes ]; then
+            NJS_CFLAGS="$NJS_CFLAGS -ffp-eval-method=double"
+        fi
+
+    ;;
+
+    SunC)
+
+        njs_found=no
+
+        njs_feature="flag -xarch=sse2"
+        njs_feature_name=NJS_HAVE_XARCH_SSE2
+        njs_feature_run=no
+        njs_feature_incs="-xarch=sse2"
+        njs_feature_libs=
+        njs_feature_test="int main(void) {
+                             return 0;
+                         }"
+
+        . auto/feature
+
+        if [ $njs_found = yes ]; then
+            NJS_CFLAGS="$NJS_CFLAGS -xarch=sse2"
+        fi
+    ;;
+
+esac
-- 
2.47.3