>From c998ae7ca5f59780f8029abdd6bf40c6581c7e49 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 2 Jul 2020 22:23:59 -0700
Subject: [PATCH] Fix AC_CHECK_LIB quoting bug

Problem reported by Bert Wesarg in:
https://lists.gnu.org/archive/html/autoconf/2016-04/msg00020.html
* lib/autoconf/libs.m4 (AC_CHECK_LIB): Fix quoting bug.
* tests/semantics.at (AC_CHECK_LIB): Add a test for the bug.
---
 lib/autoconf/libs.m4 | 2 +-
 tests/semantics.at   | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/autoconf/libs.m4 b/lib/autoconf/libs.m4
index f5828e40..becb2231 100644
--- a/lib/autoconf/libs.m4
+++ b/lib/autoconf/libs.m4
@@ -101,7 +101,7 @@ AC_DEFUN([AC_CHECK_LIB],
 [m4_ifval([$3], , [AH_CHECK_LIB([$1])])dnl
 AS_LITERAL_WORD_IF([$1],
 	      [AS_VAR_PUSHDEF([ac_Lib], [ac_cv_lib_$1_$2])],
-	      [AS_VAR_PUSHDEF([ac_Lib], [ac_cv_lib_$1''_$2])])dnl
+	      [AS_VAR_PUSHDEF([ac_Lib], [ac_cv_lib_$1""_$2])])dnl
 AC_CACHE_CHECK([for $2 in -l$1], [ac_Lib],
 [ac_check_lib_save_LIBS=$LIBS
 LIBS="-l$1 $5 $LIBS"
diff --git a/tests/semantics.at b/tests/semantics.at
index 3324a230..f10a0b53 100644
--- a/tests/semantics.at
+++ b/tests/semantics.at
@@ -42,9 +42,13 @@ ac_sin=sin
 AC_CHECK_LIB(m, $ac_sin,,
       [AC_MSG_ERROR([cannot find `\$ac_sin' (= `$ac_sin') in `libm'])])
 
+AS_UNSET([ac_cv_lib_m_acos])
 ac_m=m
 AC_CHECK_LIB($ac_m, acos,,
       [AC_MSG_ERROR([cannot find `acos' in `\$ac_m' (= `$ac_m')])])
+if test "${ac_cv_lib_m_acos+set}" != set; then
+  AC_MSG_ERROR([ac_cv_lib_m_acos not set])
+fi
 
 ac_asin=asin
 AC_CHECK_LIB($ac_m, $ac_asin,,
-- 
2.17.1