Issue #6 (library-check) improved AX_CHECK_LIB

Previous implementation of AX_CHECK_LIB macro fails whether any function
in argument list has not been found and informs only about this function.
This causes several configure runs to detect all names which has not been found.
Current implementation validates the entire list of required functions for one
library required by one component and informs about all functions that
have not been found.

Author: igormunkin

ac-macros/ax-macros.m4

@@ -41,16 +41,20 @@ AC_DEFUN([AX_RAW_CHECK_PROG], [
 # $1 - library name (without 'lib' prefix and extension suffix)
 # $2 - list of required functions
 AC_DEFUN([AX_CHECK_LIB], [
+	NOT_FOUND=''
+	CACHED_LIBS=$LIBS
 	for sub in $2
 	do
-		AC_CHECK_LIB([$1], [$sub], [
-			# The check below is necessary for deduplication of $1 library
-			# within LIBS variable
-			AS_IF([echo $LIBS | grep -q "$1"], [], [
-				AS_VAR_APPEND([LIBS], [-l$1])
-			])
-		], [
-			AC_MSG_ERROR([Function $sub does not exist in $1])
-		])
+		AC_CHECK_LIB([$1], [$sub], [ ], [ NOT_FOUND="$NOT_FOUND $sub" ])
 	done
+	AS_IF([test "x$NOT_FOUND" == "x"], [
+		# Deduplication of $1 library in LIBS: if library $1 already exists in
+		# LIBS it won't be added, otherwise new LIBS will contain CACHED_LIBS
+		# and -l$1.
+		# Rationale for this hack # is written in autoconf documentation
+		# (https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Libraries.html)
+		AS_CASE(["$LIBS"], [*"-l$1"*], [], [LIBS="$CACHED_LIBS -l$1"])
+	], [
+		AC_MSG_ERROR([Functions:$NOT_FOUND do not exist in $1])
+	])
 ])