From b5c5909f30ea68a1528b1fe24871b2e49a01f119 Mon Sep 17 00:00:00 2001
From: Marcel Raad <raad@teamviewer.com>
Date: Fri, 16 Jun 2017 14:06:23 +0200
Subject: curl-compilers.m4: enable double-promotion warning

Enable -Wdouble-promotion for both GCC and clang. It warns on implicit
promotion from float to double.

Closes https://github.com/curl/curl/pull/1578
---
 m4/curl-compilers.m4 | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/m4/curl-compilers.m4 b/m4/curl-compilers.m4
index 5860f946e..7d53953c9 100644
--- a/m4/curl-compilers.m4
+++ b/m4/curl-compilers.m4
@@ -891,6 +891,11 @@ AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
           if test "$compiler_num" -ge "209"; then
             tmp_CFLAGS="$tmp_CFLAGS -Wshift-sign-overflow"
           fi
+          #
+          dnl Only clang 3.6 or later
+          if test "$compiler_num" -ge "306"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wdouble-promotion"
+          fi
         fi
         ;;
         #
@@ -1002,6 +1007,11 @@ AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
             fi
           fi
           #
+          dnl Only gcc 4.6 or later
+          if test "$compiler_num" -ge "406"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wdouble-promotion"
+          fi
+          #
         fi
         #
         dnl Do not issue warnings for code in system include paths.
-- 
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