* lib.c (upop): New function.

* lib.h (upop): Declared.

* txr.c (txr_main): Two bugfixes. One is that the argument -
was being pushed back twice resulting in *args* being ("-" "-").
This is because the option processing loop checked for "-" and pushed
it back into args, and then some logic after the loop pushed arg back
into args again. But, these pushes were wrong because they push
back a different cons cell; we would like to be able to
do (ldiff *full-args* *args*). This is solved by upop, which provides
one element of undo. After upop, we can restore the prior list
from the undo save location.

4 files changed, 31 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index e6df860d..d9d74336 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,21 @@
 2014-03-06  Kaz Kylheku  <kaz@kylheku.com>
 
+	* lib.c (upop): New function.
+
+	* lib.h (upop): Declared.
+
+	* txr.c (txr_main): Two bugfixes. One is that the argument -
+	was being pushed back twice resulting in *args* being ("-" "-").
+	This is because the option processing loop checked for "-" and pushed
+	it back into args, and then some logic after the loop pushed arg back
+	into args again. But, these pushes were wrong because they push
+	back a different cons cell; we would like to be able to
+	do (ldiff *full-args* *args*). This is solved by upop, which provides
+	one element of undo. After upop, we can restore the prior list
+	from the undo save location.
+
+2014-03-06  Kaz Kylheku  <kaz@kylheku.com>
+
 	* lib.c (assert_s): New global variable.
 	(obj_init): Intern assert symbol, store in assert_s.
 
diff --git a/lib.c b/lib.c
index 4365c4b8..2b5bd031 100644
--- a/lib.c
+++ b/lib.c
@@ -426,6 +426,12 @@ val pop(val *plist)
   return ret;
 }
 
+val upop(val *plist, val *pundo)
+{
+  *pundo = *plist;
+  return pop(plist);
+}
+
 val push(val value, val *plist)
 {
   /* Unsafe for mutating object fields: use mpush macro. */
diff --git a/lib.h b/lib.h
index ab519088..c1524891 100644
--- a/lib.h
+++ b/lib.h
@@ -385,6 +385,7 @@ val *tail(val cons);
 val *lastcons(val list);
 val *ltail(val *cons);
 val pop(val *plist);
+val upop(val *plist, val *pundo);
 val push(val v, val *plist);
 val copy_list(val list);
 val make_like(val list, val thatobj);
diff --git a/txr.c b/txr.c
index 2e3b6ac5..9dbb0ebd 100644
--- a/txr.c
+++ b/txr.c
@@ -178,7 +178,7 @@ int txr_main(int argc, char **argv)
   val bindings = nil;
   val evaled = nil;
   int match_loglevel = opt_loglevel;
-  val arg;
+  val arg_undo = nil, arg;
   list_collect_decl(arg_list, arg_tail);
 
   prot1(&spec_file_str);
@@ -199,15 +199,15 @@ int txr_main(int argc, char **argv)
 
   arg_list = cdr(arg_list);
 
-  for (arg = pop(&arg_list); arg && car(arg) == chr('-'); arg = pop(&arg_list))
+  for (arg = upop(&arg_list, &arg_undo);
+       arg && car(arg) == chr('-');
+       arg = upop(&arg_list, &arg_undo))
   {
     if (equal(arg, lit("--")))
       break;
 
-    if (equal(arg, lit("-"))) {
-      push(arg, &arg_list);
+    if (equal(arg, lit("-")))
       break;
-    }
 
     if (equal(sub(arg, zero, two), lit("-D"))) {
       val dopt_arg = sub(arg, two, t);
@@ -247,7 +247,7 @@ int txr_main(int argc, char **argv)
         return EXIT_FAILURE;
       }
 
-      arg = pop(&arg_list);
+      arg = upop(&arg_list, &arg_undo);
 
       switch (c_chr(opt)) {
       case 'a':
@@ -383,7 +383,7 @@ int txr_main(int argc, char **argv)
       specstring = cat_str(list(specstring, string(L"\n"), nao), nil);
     yyin_stream = make_string_byte_input_stream(specstring);
     if (arg)
-      push(arg, &arg_list);
+      arg_list = arg_undo;
   } else if (spec_file) {
     if (wcscmp(c_str(spec_file), L"-") != 0) {
       FILE *in = w_fopen(c_str(spec_file), L"r");
@@ -395,7 +395,7 @@ int txr_main(int argc, char **argv)
       spec_file_str = lit("stdin");
     }
     if (arg)
-      push(arg, &arg_list);
+      arg_list = arg_undo;
   } else {
     if (!arg) {
       if (evaled)