fix guile-snarf

* libguile/snarf.h: New macro `SCM_SNARF_INIT_PREFIX'. (SCM_SNARF_INIT)
  Use `SCM_SNARF_INIT_PREFIX' instead of including a literal marker. If
  the preprocessor echoes #define directives to its output, this will
  prevent `guile-snarf' from snarfing the `SCM_SNARF_INIT' definition
  itself. Reported by Mike Gran <spk121@yahoo.com>.
* libguile/guile-snarf.in (modern_snarf): Don't output anything for
  lines in which only one of the magic snarfing markers is present.
  Modify the `sed' program for compatibility with POSIX `sed'. The new
  `sed' program is based on a version by Wolfgang Jenkner
  <wjenkner@inode.at>.
* test-suite/standalone/test-guile-snarf: New tests.

libguile/guile-snarf.in

@@ -51,7 +51,20 @@ modern_snarf ()                         # writes stdout
     ## empty file.
     echo "/* cpp arguments: $@ */" ;
     ${cpp} -DSCM_MAGIC_SNARF_INITS -DSCM_MAGIC_SNARFER "$@" > ${temp} && cpp_ok_p=true
-    sed -ne "s/ *\^ *: *\^/\n/;s/[^\n]*\^ *\^ *\([^\n]*\)/\1;/;tx;d;:x;P;D" ${temp}
+    sed -ne 's/ *\^ *: *\^/\
+/
+h
+s/\n.*//
+t x
+d
+: x
+s/.*\^ *\^ *\(.*\)/\1;/
+t y
+d
+: y
+p
+x
+D' ${temp}
 }
 
 ## main

libguile/snarf.h

@@ -53,11 +53,17 @@
  * The SCM_SNARF_INIT text goes into the corresponding .x file
  * up through the first occurrence of SCM_SNARF_DOC_START on that
  * line, if any.
+ *
+ * Some debugging options can cause the preprocessor to echo #define
+ * directives to its output. Keeping the snarfing markers on separate
+ * lines prevents guile-snarf from inadvertently snarfing the definition
+ * of SCM_SNARF_INIT if those options are in effect.
  */
 
 #ifdef SCM_MAGIC_SNARF_INITS
 # define SCM_SNARF_HERE(X)
-# define SCM_SNARF_INIT(X) ^^ X ^:^
+# define SCM_SNARF_INIT_PREFIX ^^
+# define SCM_SNARF_INIT(X) SCM_SNARF_INIT_PREFIX X ^:^
 # define SCM_SNARF_DOCS(TYPE, CNAME, FNAME, ARGLIST, REQ, OPT, VAR, DOCSTRING)
 #else
 # ifdef SCM_MAGIC_SNARF_DOCS

test-suite/standalone/test-guile-snarf

@@ -18,3 +18,5 @@ snarf_test "  ^  ^  b  ^  :  ^  " "b;"
 snarf_test "c\n^^d^:^\ne" "d;"
 snarf_test "f^^g^:^h" "g;"
 snarf_test "^^i^:^j^^k^:^" "i;k;"
+snarf_test "l^^m" ""
+snarf_test "n^:^o" ""