fixed serious bug with certain alternative string termination chars in commands with multiple string arguments

* When `@`-modifying a command with several string arguments and choosing `{` as the alternative
  string termination character, the parser would get totally confused.
  Any sequence of `{` would be ignored and only the first non-`{` would become the termination character.
  Consequently you also couldn't choose a new terminator after the closing `}`.
  So even a documented code example from sciteco(7) wouldn't work.
  The same was true when using $ (escape) or ^A as the alternative termination character.
* We can now correctly parse e.g. `@FR{foo}{bar}` or `@FR$foo$bar$` (even though the
  latter one is quite pointless).
* has probably been broken forever (has been broken even before v2.0).
* Whitespace is now ignored in front of alternative termination characters as in TECO-64, so
  we can also write `@S /foo/` or even
  ```
  @^Um
  {
    !* blabla *!
  }
  ```
  I wanted to disallow whitespace termination characters, so the alternative would have been
  to throw an error.
  The new implementation at least adds some functionality.
  * Avoid redundancies when parsing no-op characters via teco_is_noop().
    I assume that this is inlined and drawn into any jump-table what would be
    generated for the switch-statement in teco_state_start_input().
 * Alternative termination characters are still case-folded, even if they are Unicode glyphs,
   so `@IЖfooж` would work and insert `foo`.
   This should perhaps be restricted to ANSI characters?

1 files changed, 6 insertions, 2 deletions

diff --git a/src/core-commands.h b/src/core-commands.h
index bf73b8c..cb28dce 100644
--- a/src/core-commands.h
+++ b/src/core-commands.h
@@ -22,8 +22,12 @@
 #include "parser.h"
 #include "string-utils.h"
 
-/** non-operational characters in teco_state_start */
-#define TECO_NOOPS " \f\r\n\v"
+/** Check whether c is a non-operational command in teco_state_start */
+static inline gboolean
+teco_is_noop(gunichar c)
+{
+	return c == ' ' || c == '\f' || c == '\r' || c == '\n' || c == '\v';
+}
 
 gboolean teco_get_range_args(const gchar *cmd, gsize *from_ret, gsize *len_ret, GError **error);