check for iconveh values at configure-time

* configure.ac: Check for the iconveh values here, instead of relying on
  gen-scmconfig to know them.  That doesn't work in general because
  gen-scmconfig runs on the build machine, not the target machine.

* libguile/Makefile.am (gen-scmconfig.$(OBJEXT)): Revert rule to the
  revision before 533d8212.

* libguile/gen-scmconfig.h.in (SCM_I_GSC_ICONVEH_ERROR):
  (SCM_I_GSC_ICONVEH_QUESTION_MARK):
  (SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE):
* libguile/gen-scmconfig.c: Use configure-time substitutions to set
  SCM_ICONVEH_ERROR_HANDLER et al.

configure.ac

@@ -1191,6 +1191,70 @@ AC_CHECK_MEMBERS([struct tm.tm_gmtoff],,,
 GUILE_STRUCT_UTIMBUF
 
 
+#--------------------------------------------------------------------
+#
+# What values do the iconv error handlers have?
+#
+# The only place that we need iconv in our public interfaces is for
+# the error handlers, which are just ints.  So we weaken our
+# dependency by looking up those values at configure-time.
+#--------------------------------------------------------------------
+SCM_I_GSC_ICONVEH_ERROR=0
+SCM_I_GSC_ICONVEH_QUESTION_MARK=1
+SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE=2
+AC_MSG_CHECKING([for iconveh_error])
+AC_RUN_IFELSE([AC_LANG_SOURCE(
+[AC_INCLUDES_DEFAULT
+#include <uniconv.h>
+int
+main (int argc, char *argv[])
+{
+  if (argc > 1)
+    printf ("%d\n", (int)iconveh_error);
+  return 0;
+}])],
+	       [SCM_I_GSC_ICONVEH_ERROR=`./conftest$EXEEXT pretty-please`
+                AC_MSG_RESULT([$SCM_I_GSC_ICONVEH_ERROR])],
+	       [AC_MSG_FAILURE([failed to get iconveh_error])],
+	       [AC_MSG_WARN([assuming $SCM_I_GSC_ICONVEH_ERROR for cross-compilation])])
+
+AC_MSG_CHECKING([for iconveh_question_mark])
+AC_RUN_IFELSE([AC_LANG_SOURCE(
+[AC_INCLUDES_DEFAULT
+#include <uniconv.h>
+int
+main (int argc, char *argv[])
+{
+  if (argc > 1)
+    printf ("%d\n", (int)iconveh_question_mark);
+  return 0;
+}])],
+	       [SCM_I_GSC_ICONVEH_QUESTION_MARK=`./conftest$EXEEXT pretty-please`
+                AC_MSG_RESULT([$SCM_I_GSC_ICONVEH_QUESTION_MARK])],
+	       [AC_MSG_FAILURE([failed to get iconveh_question_mark])],
+	       [AC_MSG_WARN([assuming $SCM_I_GSC_ICONVEH_QUESTION_MARK for cross-compilation])])
+
+AC_MSG_CHECKING([for iconveh_escape_sequence])
+AC_RUN_IFELSE([AC_LANG_SOURCE(
+[AC_INCLUDES_DEFAULT
+#include <uniconv.h>
+int
+main (int argc, char *argv[])
+{
+  if (argc > 1)
+    printf ("%d\n", (int)iconveh_escape_sequence);
+  return 0;
+}])],
+	       [SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE=`./conftest$EXEEXT pretty-please`
+                AC_MSG_RESULT([$SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE])],
+	       [AC_MSG_FAILURE([failed to get iconveh_escape_sequence])],
+	       [AC_MSG_WARN([assuming $SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE for cross-compilation])])
+
+AC_SUBST([SCM_I_GSC_ICONVEH_ERROR])
+AC_SUBST([SCM_I_GSC_ICONVEH_QUESTION_MARK])
+AC_SUBST([SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE])
+
+
 #--------------------------------------------------------------------
 #
 # Which way does the stack grow?

libguile/Makefile.am

@@ -57,9 +57,7 @@ gen_scmconfig_SOURCES = gen-scmconfig.c
 gen-scmconfig.$(OBJEXT): gen-scmconfig.c
 	$(AM_V_GEN) \
 	if [ "$(cross_compiling)" = "yes" ]; then \
-		$(CC_FOR_BUILD) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES)	\
+		$(CC_FOR_BUILD) $(DEFS) $(DEFAULT_INCLUDES) $(AM_CPPFLAGS) -c -o $@ $<; \
-		  $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)	\
-	          -c -o $@ $<;						\
 	else \
 		$(COMPILE) -c -o $@ $<; \
 	fi

libguile/gen-scmconfig.c

@@ -123,7 +123,6 @@
 
 #include <stdio.h>
 #include <string.h>
-#include <uniconv.h>
 
 #define pf printf
 
@@ -397,11 +396,11 @@ main (int argc, char *argv[])
 
   pf ("\n");
   pf ("/* Constants from uniconv.h.  */\n");
-  pf ("#define SCM_ICONVEH_ERROR %d\n", (int) iconveh_error);
+  pf ("#define SCM_ICONVEH_ERROR %d\n", SCM_I_GSC_ICONVEH_ERROR);
   pf ("#define SCM_ICONVEH_QUESTION_MARK %d\n",
-      (int) iconveh_question_mark);
+      SCM_I_GSC_ICONVEH_QUESTION_MARK);
   pf ("#define SCM_ICONVEH_ESCAPE_SEQUENCE %d\n",
-      (int) iconveh_escape_sequence);  
+      SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE);  
 
   printf ("#endif\n");
 

libguile/gen-scmconfig.h.in

@@ -31,6 +31,9 @@
 #define SCM_I_GSC_NEED_BRACES_ON_PTHREAD_MUTEX_INITIALIZER @SCM_I_GSC_NEED_BRACES_ON_PTHREAD_MUTEX_INITIALIZER@
 #define SCM_I_GSC_HAVE_THREAD_STORAGE_CLASS @SCM_I_GSC_HAVE_THREAD_STORAGE_CLASS@
 #define SCM_I_GSC_HAVE_STRUCT_DIRENT64 @SCM_I_GSC_HAVE_STRUCT_DIRENT64@
+#define SCM_I_GSC_ICONVEH_ERROR @SCM_I_GSC_ICONVEH_ERROR@
+#define SCM_I_GSC_ICONVEH_QUESTION_MARK @SCM_I_GSC_ICONVEH_QUESTION_MARK@
+#define SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE @SCM_I_GSC_ICONVEH_ESCAPE_SEQUENCE@
 
 /*
   Local Variables: