Require GMP and take GAP's GMP_PREFIX into account

There is no good reason to allow building anupq without GMP
these days. On the downside, if one fails to do that (which may
happen without the user even knowing what happened), one may get
unexpected errors or perhaps even wrong results. So better to
just require this.

This also simplifies the logic in configure.ac considerably,
and allows us to just use the same as in anunq.

Makefile.am

@@ -30,6 +30,7 @@ PQFLAGS += -DANUPQ_GAP_EXEC='"@GAP_EXEC@"'
 
 bin_PROGRAMS = pq
 
+pq_LDFLAGS = $(GMP_LDFLAGS)
 pq_LDADD = $(GMP_LIBS)
 pq_CPPFLAGS = $(GMP_CPPFLAGS) $(PQFLAGS)
 

configure.ac

@@ -42,100 +42,74 @@ FIND_GAP
 
 dnl ##
 dnl ## Check for GMP
-dnl ## If the user specified a specific GMP, try to use that.
-dnl ## Otherwise, first try to use the GMP provided by GAP, or
-dnl ## any GMP version installed globally by the user.
 dnl ##
 
-GMP_CPPFLAGS=
-GMP_LIBS=
-
 AC_ARG_WITH([gmp],
-	[AS_HELP_STRING([--with-gmp=PATH],
-	  [ Use GMP library.
-        If the argument you supply is "yes" or <empty>, then the version of GMP bundled with GAP will be used (default).
-        If the argument is "system" that means the library is reachable with the standard
-        search path "/usr" or "/usr/local".
-        Otherwise you give the <path> to the directory which contains the library.
-        [[default=yes]]
-    ])],
-  [], [ with_gmp=yes ]
-)
+  [AS_HELP_STRING([--with-gmp@<:@=PREFIX@:>@],
+    [prefix of GMP installation. e.g. /usr/local])],
+    [],[with_gmp=${GMP_PREFIX}])
+
+GMP_CPPFLAGS=""
+GMP_LDFLAGS=""
+GMP_LIBS="-lgmp"
 
 if test "x$with_gmp" = "xno" ; then
-	AC_MSG_NOTICE([Building without GMP support])
-elif test "x$with_gmp" = "xsystem" ; then
-	# Try using system GMP
-	GMP_CPPFLAGS=""
-	GMP_LIBS="-lgmp"
+	AC_MSG_ERROR([GMP is required and cannot be disabled])
+elif test "x$with_gmp" = "xyes" ; then
+    # If a gaproot was specified, try to find GMP in there; otherwise, fall
+    # back to whatever GMP may be found via user specified C/CPP/LDFLAGS
+    if test "${with_gaproot+set}" = set; then
+        echo "with_gaproot = $with_gaproot"
+        if test -f ${with_gaproot}/extern/install/gmp/include/gmp.h && test -d ${with_gaproot}/extern/install/gmp/lib ; then
+            echo "adjusting stuff based on gaproot"
+            GMP_CPPFLAGS="-I${with_gaproot}/extern/install/gmp/include"
+            GMP_LDFLAGS="-L${with_gaproot}/extern/install/gmp/lib"
+        fi
+    fi
 else
-	# Try using static linked GMP in the specified location
-	if test "x$with_gmp" = "xyes" ; then
-		# Try to use GAP's GMP, if available
-        GMP_HOME="$GAPROOT/extern/install/gmp"
+	if test -d ${with_gmp}/include && test -d ${with_gmp}/lib ; then
+		GMP_CPPFLAGS="-I${with_gmp}/include"
+        GMP_LDFLAGS="-L${with_gmp}/lib"
 	else
-		GMP_HOME="$with_gmp"
-	fi;
-	if test -d ${GMP_HOME}/include && test -d ${GMP_HOME}/lib ; then
-		GMP_CPPFLAGS="-I${GMP_HOME}/include"
-		# gross hack follows
-		if test -r "${GMP_HOME}/lib/libgmp.a" ; then
-			GMP_LIBS="${GMP_HOME}/lib/libgmp.a"
-		elif test -r "${GMP_HOME}/lib/libgmp.dylib" ; then
-			GMP_LIBS="${GMP_HOME}/lib/libgmp.dylib"
-		elif test -r "${GMP_HOME}/lib/libgmp.so" ; then
-			GMP_LIBS="${GMP_HOME}/lib/libgmp.so"
-		else
-			# generic fallback -- unfortunately, this does not ensure that we
-			# link against exactly that version of libgmp
-			GMP_LIBS="-L${GMP_HOME}/lib -lgmp"
-		fi
-	elif test "x$with_gmp" = "xyes" ; then
-		# fallback to trying system wide GMP
-		GMP_CPPFLAGS=""
-		GMP_LIBS="-lgmp"
-	else
-		AC_MSG_ERROR([Could not locate libgmp.a in the specified location])
+		AC_MSG_ERROR([Could not locate libgmp in the specified location])
 	fi
 fi;
 
-have_gmp=no
-if test "x$with_gmp" != xno; then
-	pq_save_CPPFLAGS="$CPPFLAGS"
-	CPPFLAGS="$CPPFLAGS $GMP_CPPFLAGS"
-	pq_save_LIBS="$LIBS"
-	LIBS="$LIBS $GMP_LIBS"
-
-	AC_CHECK_HEADER( [gmp.h],
-		[
-		# TODO: Disable linker check for now: It causes problems on Linux, because
-		# libgmp.a is in the linker command line before the test C file. On the long
-		# run, this should be re-enabled, though perhaps in a different form.
-		AC_MSG_CHECKING([whether linking against GMP works])
-		AC_LINK_IFELSE(
-			[AC_LANG_PROGRAM([[#include <gmp.h>]], [[__gmpz_init(0);]])],
-			[have_gmp=yes],
-			[]
-			)
-		AC_MSG_RESULT([$have_gmp])
-		],
-		[]
-		)
-
-	# restore FLAGS
-	CPPFLAGS="$pq_save_CPPFLAGS"
-	LIBS="$pq_save_LIBS"
-
-fi;
-
-if test "x$have_gmp" = xyes; then
-	AC_DEFINE(HAVE_GMP, 1, [Define if GMP is installed and usable])
-else
-GMP_CPPFLAGS=""
-GMP_LIBS=""
+save_CPPFLAGS="$CPPFLAGS"
+save_LDFLAGS="$LDFLAGS"
+save_LIBS="$LIBS"
+
+CPPFLAGS="$CPPFLAGS $GMP_CPPFLAGS"
+LDFLAGS="$LDFLAGS $GMP_LDFLAGS"
+LIBS="$LIBS $GMP_LIBS"
+
+AC_CHECK_HEADER( [gmp.h],
+    [
+    # TODO: Disable linker check for now: It causes problems on Linux, because
+    # libgmp.a is in the linker command line before the test C file. On the long
+    # run, this should be re-enabled, though perhaps in a different form.
+    AC_MSG_CHECKING([whether linking against GMP works])
+    AC_LINK_IFELSE(
+        [AC_LANG_PROGRAM([[#include <gmp.h>]], [[__gmpz_init(0);]])],
+        [have_gmp=yes],
+        []
+        )
+    AC_MSG_RESULT([$have_gmp])
+    ],
+    []
+    )
+
+# restore FLAGS
+CPPFLAGS="$save_CPPFLAGS"
+LDFLAGS="$save_LDFLAGS"
+LIBS="$save_LIBS"
+
+if test "x$have_gmp" != xyes; then
+    AC_MSG_ERROR([Could not locate GMP, the GNU multiprecision library])
 fi
 
 AC_SUBST(GMP_CPPFLAGS)
+AC_SUBST(GMP_LDFLAGS)
 AC_SUBST(GMP_LIBS)
 
 dnl ##