Avoid keeping pointers from `mrb_sym2name_len()`; fix #4342

The addresses for packed inline symbols reference `mrb->symbuf` that
could be overridden by the later call of `mrb_sym2name_len`. Since
file names in call stack information are kept as symbols, keeping the
address in the C structures could cause problems like #4342.

This changes small incompatible changes in function prototypes:
* `mrb_parser_get_filename`: return value changed to `mrb_sym`.
* `mrb_debug_get_filename`: add `mrb_state*` as a first argument.
* `mrb_debug_get_line`: ditto.

I believe above functions are almost internal, and no third-party
mrbgem use them.

2 files changed, 25 insertions, 20 deletions

diff --git a/mrbgems/mruby-compiler/core/codegen.c b/mrbgems/mruby-compiler/core/codegen.c
index a2d790e32..927cc3a0f 100644
--- a/mrbgems/mruby-compiler/core/codegen.c
+++ b/mrbgems/mruby-compiler/core/codegen.c
@@ -62,7 +62,7 @@ typedef struct scope {
 
   struct loopinfo *loop;
   int ensure_level;
-  char const *filename;
+  mrb_sym filename_sym;
   uint16_t lineno;
 
   mrb_code *iseq;
@@ -106,8 +106,9 @@ codegen_error(codegen_scope *s, const char *message)
     s = tmp;
   }
 #ifndef MRB_DISABLE_STDIO
-  if (s->filename && s->lineno) {
-    fprintf(stderr, "codegen error:%s:%d: %s\n", s->filename, s->lineno, message);
+  if (s->filename_sym && s->lineno) {
+    const char *filename = mrb_sym2name_len(s->mrb, s->filename_sym, NULL);
+    fprintf(stderr, "codegen error:%s:%d: %s\n", filename, s->lineno, message);
   }
   else {
     fprintf(stderr, "codegen error: %s\n", message);
@@ -1399,13 +1400,14 @@ codegen(codegen_scope *s, node *tree, int val)
     codegen_error(s, "too complex expression");
   }
   if (s->irep && s->filename_index != tree->filename_index) {
-    const char *filename = mrb_parser_get_filename(s->parser, s->filename_index);
+    mrb_sym fname = mrb_parser_get_filename(s->parser, s->filename_index);
+    const char *filename = mrb_sym2name_len(s->mrb, fname, NULL);
 
     mrb_debug_info_append_file(s->mrb, s->irep->debug_info,
                                filename, s->lines, s->debug_start_pos, s->pc);
     s->debug_start_pos = s->pc;
     s->filename_index = tree->filename_index;
-    s->filename = mrb_parser_get_filename(s->parser, tree->filename_index);
+    s->filename_sym = mrb_parser_get_filename(s->parser, tree->filename_index);
   }
 
   nt = nint(tree->car);
@@ -2990,15 +2992,15 @@ scope_new(mrb_state *mrb, codegen_scope *prev, node *lv)
   }
   p->ai = mrb_gc_arena_save(mrb);
 
-  p->filename = prev->filename;
-  if (p->filename) {
+  p->filename_sym = prev->filename_sym;
+  if (p->filename_sym) {
     p->lines = (uint16_t*)mrb_malloc(mrb, sizeof(short)*p->icapa);
   }
   p->lineno = prev->lineno;
 
   /* debug setting */
   p->debug_start_pos = 0;
-  if (p->filename) {
+  if (p->filename_sym) {
     mrb_debug_info_alloc(mrb, p->irep);
   }
   else {
@@ -3026,8 +3028,9 @@ scope_finish(codegen_scope *s)
   irep->pool = (mrb_value*)codegen_realloc(s, irep->pool, sizeof(mrb_value)*irep->plen);
   irep->syms = (mrb_sym*)codegen_realloc(s, irep->syms, sizeof(mrb_sym)*irep->slen);
   irep->reps = (mrb_irep**)codegen_realloc(s, irep->reps, sizeof(mrb_irep*)*irep->rlen);
-  if (s->filename) {
-    const char *filename = mrb_parser_get_filename(s->parser, s->filename_index);
+  if (s->filename_sym) {
+    mrb_sym fname = mrb_parser_get_filename(s->parser, s->filename_index);
+    const char *filename = mrb_sym2name_len(s->mrb, fname, NULL);
 
     mrb_debug_info_append_file(s->mrb, s->irep->debug_info,
                                filename, s->lines, s->debug_start_pos, s->pc);
@@ -3136,7 +3139,7 @@ generate_code(mrb_state *mrb, parser_state *p, int val)
   }
   scope->mrb = mrb;
   scope->parser = p;
-  scope->filename = p->filename;
+  scope->filename_sym = p->filename_sym;
   scope->filename_index = p->current_filename_index;
 
   MRB_TRY(&scope->jmp) {
diff --git a/mrbgems/mruby-compiler/core/parse.y b/mrbgems/mruby-compiler/core/parse.y
index 90f01e3a8..88d9ea4ee 100644
--- a/mrbgems/mruby-compiler/core/parse.y
+++ b/mrbgems/mruby-compiler/core/parse.y
@@ -3162,7 +3162,7 @@ var_ref         : variable
                     }
                 | keyword__FILE__
                     {
-                      const char *fn = p->filename;
+                      const char *fn = mrb_sym2name_len(p->mrb, p->filename_sym, NULL);
                       if (!fn) {
                         fn = "(null)";
                       }
@@ -3671,8 +3671,9 @@ yyerror(parser_state *p, const char *s)
 
   if (! p->capture_errors) {
 #ifndef MRB_DISABLE_STDIO
-    if (p->filename) {
-      fprintf(stderr, "%s:%d:%d: %s\n", p->filename, p->lineno, p->column, s);
+    if (p->filename_sym) {
+      const char *filename = mrb_sym2name_len(p->mrb, p->filename_sym, NULL);
+      fprintf(stderr, "%s:%d:%d: %s\n", filename, p->lineno, p->column, s);
     }
     else {
       fprintf(stderr, "line %d:%d: %s\n", p->lineno, p->column, s);
@@ -3707,8 +3708,9 @@ yywarn(parser_state *p, const char *s)
 
   if (! p->capture_errors) {
 #ifndef MRB_DISABLE_STDIO
-    if (p->filename) {
-      fprintf(stderr, "%s:%d:%d: warning: %s\n", p->filename, p->lineno, p->column, s);
+    if (p->filename_sym) {
+      const char *filename = mrb_sym2name_len(p->mrb, p->filename_sym, NULL);
+      fprintf(stderr, "%s:%d:%d: warning: %s\n", filename, p->lineno, p->column, s);
     }
     else {
       fprintf(stderr, "line %d:%d: warning: %s\n", p->lineno, p->column, s);
@@ -6012,7 +6014,7 @@ mrb_parser_set_filename(struct mrb_parser_state *p, const char *f)
   mrb_sym* new_table;
 
   sym = mrb_intern_cstr(p->mrb, f);
-  p->filename = mrb_sym2name_len(p->mrb, sym, NULL);
+  p->filename_sym = sym;
   p->lineno = (p->filename_table_length > 0)? 0 : 1;
 
   for (i = 0; i < p->filename_table_length; ++i) {
@@ -6036,11 +6038,11 @@ mrb_parser_set_filename(struct mrb_parser_state *p, const char *f)
   p->filename_table[p->filename_table_length - 1] = sym;
 }
 
-MRB_API char const*
+MRB_API mrb_sym
 mrb_parser_get_filename(struct mrb_parser_state* p, uint16_t idx) {
-  if (idx >= p->filename_table_length) return NULL;
+  if (idx >= p->filename_table_length) return 0;
   else {
-    return mrb_sym2name_len(p->mrb, p->filename_table[idx], NULL);
+    return p->filename_table[idx];
   }
 }