pragma: handle default name/fallback handler for NULL list; cleanups

The previous code would fail to process any directive if the directive
list was NULL. However, we also need to process the default name
passed to search_pragma_list() (e.g. "elf32"), as well as the global
name (e.g. "output") and call the default handler in that case.

In the process, improve the handling such that if one handler returns
DIRR_UNKNOWN, try calling subsequent handlers in the list.

Finally, factor out as much as possible to generic handlers.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

asm/pragma.c

@@ -47,7 +47,9 @@
 #include "error.h"
 #include "listing.h"
 
+static enum directive_result ignore_pragma(const struct pragma *pragma);
 static enum directive_result output_pragma(const struct pragma *pragma);
+static enum directive_result debug_pragma(const struct pragma *pragma);
 static enum directive_result limit_pragma(const struct pragma *pragma);
 
 /*
@@ -90,68 +92,114 @@ static struct pragma_facility global_pragmas[] =
     { "list",		list_pragma },
     { "file",		NULL },
     { "input",		NULL },
+    { "output",		output_pragma },
+    { "debug",	        debug_pragma },
+    { "ignore",		ignore_pragma },
 
-    /* None of these should actually happen due to special handling */
+    /* This will never actually get this far... */
     { "preproc",	NULL }, /* Handled in the preprocessor by necessity */
-    { "output",		NULL },
-    { "debug",	        NULL },
-    { "ignore",		NULL },
     { NULL, NULL }
 };
 
 /*
- * Search a pragma list for a known pragma facility and if so, invoke
+ * Invoke a pragma handler
- * the handler.  Return true if processing is complete.
- * The "default name", if set, matches the final NULL entry (used
- * for backends, so multiple backends can share the same list under
- * some circumstances.)
  */
-static bool search_pragma_list(const struct pragma_facility *list,
+static enum directive_result
-                               const char *default_name,
+call_pragma(const struct pragma_facility *pf, struct pragma *pragma)
-                               pragma_handler generic_handler,
-			       struct pragma *pragma)
 {
-    const struct pragma_facility *pf;
+    if (!pf || !pf->handler)
-    enum directive_result rv;
+        return DIRR_UNKNOWN;
 
-    if (!list)
+    pragma->facility = pf;
-	return false;
+    return pf->handler(pragma);
-
-    for (pf = list; pf->name; pf++) {
-        if (!nasm_stricmp(pragma->facility_name, pf->name))
-            goto found_it;
 }
 
-    if (default_name && !nasm_stricmp(pragma->facility_name, default_name))
+/*
-        goto found_it;
+ * Search a pragma list for a known pragma facility and if so, invoke
+ * the handler.  Return true if processing is complete.  The "default
+ * name", *or def->name*, if set, matches the final NULL entry (used
+ * for backends, so multiple backends can share the same list under
+ * some circumstances, and the backends can implement common operations.)
+ */
+static enum directive_result
+search_pragma_list(const struct pragma_facility *list,
+                   const char *defaultname,
+                   const struct pragma_facility *def,
+                   const struct pragma *cpragma)
+{
+    const struct pragma_facility *pf = NULL;
+    enum directive_result rv;
+    bool facility_match, is_default;
+    struct pragma pragma = *cpragma;
+    const char *facname = pragma.facility_name;
 
-    return false;
+    /* Is there a default facility and we match its name? */
+    is_default = def && def->name && !nasm_stricmp(facname, def->name);
+    facility_match = is_default;
+
+    /*
+     * Promote def->name to defaultname if both are set. This handles
+     * e.g. output -> elf32 so that we can handle elf32-specific
+     * directives in that handler.
+     */
+    if (defaultname) {
+        if (is_default)
+            facname = defaultname;
+        else
+            facility_match = !nasm_stricmp(facname, defaultname);
+    }
+
+    if (facname && list) {
+        for (pf = list; pf->name; pf++) {
+            if (!nasm_stricmp(facname, pf->name)) {
+                facility_match = true;
+                rv = call_pragma(pf, &pragma);
+                if (rv != DIRR_UNKNOWN)
+                    goto found_it;
+            }
+        }
+
+        if (facility_match) {
+            /*
+             * Facility name match but no matching directive; handler in NULL
+             * entry at end of list?
+             */
+            rv = call_pragma(pf, &pragma);
+            if (rv != DIRR_UNKNOWN)
+                goto found_it;
+        }
+    }
+
+    if (facility_match) {
+        /*
+         * Facility match but still nothing: def->handler if it exists
+         */
+        rv = call_pragma(def, &pragma);
+    } else {
+        /*
+         * No facility matched
+         */
+        return DIRR_UNKNOWN;
+    }
+
+    /*
+     * Otherwise we found the facility but not any supported directive,
+     * fall through...
+     */
 
 found_it:
-    pragma->facility = pf;
-
-    /* If the handler is NULL all pragmas are unknown... */
-    if (pf->handler)
-        rv = pf->handler(pragma);
-    else
-        rv = DIRR_UNKNOWN;
-
-    /* Is there an additional, applicable generic handler? */
-    if (rv == DIRR_UNKNOWN && generic_handler)
-        rv = generic_handler(pragma);
-
     switch (rv) {
     case DIRR_UNKNOWN:
-        switch (pragma->opcode) {
+        switch (pragma.opcode) {
         case D_none:
             /*!
-             *!pragma-bad [off] empty or malformed %pragma
+             *!pragma-bad [off] malformed %pragma
              *!=bad-pragma
              *!  warns about a malformed or otherwise unparsable
              *!  \c{%pragma} directive.
              */
             nasm_warn(ERR_PASS2|WARN_PRAGMA_BAD,
-                       "empty %%pragma %s", pragma->facility_name);
+                       "empty %%pragma %s", pragma.facility_name);
             break;
         default:
             /*!
@@ -162,9 +210,10 @@ found_it:
              */
             nasm_warn(ERR_PASS2|WARN_PRAGMA_UNKNOWN,
                        "unknown %%pragma %s %s",
-                       pragma->facility_name, pragma->opname);
+                       pragma.facility_name, pragma.opname);
             break;
         }
+        rv = DIRR_ERROR;        /* Already printed an error message */
         break;
 
     case DIRR_OK:
@@ -177,13 +226,13 @@ found_it:
          * would be compromised, as opposed to an inherent error.
          */
         nasm_error(ERR_NONFATAL, "bad argument to %%pragma %s %s",
-                   pragma->facility_name, pragma->opname);
+                   pragma.facility_name, pragma.opname);
         break;
 
     default:
         panic();
     }
-    return true;
+    return rv;
 }
 
 /* This warning message is intended for future use */
@@ -194,8 +243,16 @@ found_it:
  *!  this particular assembly session.  This is not yet implemented.
  */
 
+/* Naked %pragma */
+/*!
+ *!pragma-empty [off] empty %pragma directive
+ *!  warns about a \c{%pragma} directive containing nothing.
+ *!  This is treated identically to \c{%pragma ignore} except
+ *!  for this optional warning.
+ */
 void process_pragma(char *str)
 {
+    const struct pragma_facility *pf;
     struct pragma pragma;
     char *p;
 
@@ -203,26 +260,11 @@ void process_pragma(char *str)
 
     pragma.facility_name = nasm_get_word(str, &p);
     if (!pragma.facility_name) {
-	nasm_warn(ERR_PASS2|WARN_PRAGMA_BAD,
+        /* Empty %pragma */
-		   "empty pragma directive");
+	nasm_warn(ERR_PASS2|WARN_PRAGMA_EMPTY,
-        return;                 /* Empty pragma */
+		   "empty %%pragma directive, ignored");
-    }
-
-    /*
-     * The facility "ignore" means just that; don't even complain of
-     * the absence of an operation.
-     */
-    if (!nasm_stricmp(pragma.facility_name, "ignore"))
         return;
-
+    }
-    /*
-     * The "output" and "debug" facilities are aliases for the
-     * current output and debug formats, respectively.
-     */
-    if (!nasm_stricmp(pragma.facility_name, "output"))
-        pragma.facility_name = ofmt->shortname;
-    if (!nasm_stricmp(pragma.facility_name, "debug"))
-        pragma.facility_name = dfmt->shortname;
 
     pragma.opname = nasm_get_word(p, &p);
     if (!pragma.opname)
@@ -232,17 +274,24 @@ void process_pragma(char *str)
 
     pragma.tail = nasm_trim_spaces(p);
 
-    /* Look for a global pragma namespace */
+    /*
-    if (search_pragma_list(global_pragmas, NULL, NULL, &pragma))
+     * Search the global pragma namespaces. This is done
+     * as a loop rather than than letting search_pragma_list()
+     * just run, because we don't want to keep searching if
+     * we have a facility match, thus we want to call
+     * search_pragma_list() individually for each namespace.
+     */
+    for (pf = global_pragmas; pf->name; pf++) {
+        if (search_pragma_list(NULL, NULL, pf, &pragma) != DIRR_UNKNOWN)
+            return;
+    }
+
+    /* Is it an output pragma? */
+    if (output_pragma(&pragma) != DIRR_UNKNOWN)
         return;
 
-    /* Look to see if it is an output backend pragma */
+    /* Is it a debug pragma */
-    if (search_pragma_list(ofmt->pragmas, ofmt->shortname,
+    if (debug_pragma(&pragma) != DIRR_UNKNOWN)
-                           output_pragma, &pragma))
-	return;
-
-    /* Look to see if it is a debug format pragma */
-    if (search_pragma_list(dfmt->pragmas, dfmt->shortname, NULL, &pragma))
         return;
 
     /*
@@ -257,11 +306,30 @@ void process_pragma(char *str)
      */
 }
 
+/* %pragma ignore */
+static enum directive_result ignore_pragma(const struct pragma *pragma)
+{
+    (void)pragma;
+    return DIRR_OK;             /* Even for D_none! */
+}
+
 /*
- * Generic pragmas that apply to all output backends; these are handled
+ * Process output and debug pragmas, by either list name or generic
- * specially so they can be made selective based on the output format.
+ * name. Note that the output/debug format list can hook the default
+ * names if they so choose.
  */
+static enum directive_result output_pragma_common(const struct pragma *);
 static enum directive_result output_pragma(const struct pragma *pragma)
+{
+    static const struct pragma_facility
+        output_pragma_def = { "output", output_pragma_common };
+
+    return search_pragma_list(ofmt->pragmas, ofmt->shortname,
+                              &output_pragma_def, pragma);
+}
+
+/* Generic pragmas that apply to all output backends */
+static enum directive_result output_pragma_common(const struct pragma *pragma)
 {
     switch (pragma->opcode) {
     case D_PREFIX:
@@ -283,6 +351,15 @@ static enum directive_result output_pragma(const struct pragma *pragma)
     }
 }
 
+static enum directive_result debug_pragma(const struct pragma *pragma)
+{
+    static const struct pragma_facility
+        debug_pragma_def = { "debug", NULL };
+
+    return search_pragma_list(dfmt->pragmas, dfmt->shortname,
+                              &debug_pragma_def, pragma);
+}
+
 /*
  * %pragma limit to set resource limits
  */