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.

7 files changed, 29 insertions, 34 deletions

diff --git a/src/backtrace.c b/src/backtrace.c
index efca2562f..e4f5a3064 100644
--- a/src/backtrace.c
+++ b/src/backtrace.c
@@ -58,10 +58,10 @@ each_backtrace(mrb_state *mrb, ptrdiff_t ciidx, mrb_code *pc0, each_backtrace_fu
       pc = pc0;
     }
 
-    loc.lineno = mrb_debug_get_line(irep, pc - irep->iseq);
+    loc.lineno = mrb_debug_get_line(mrb, irep, pc - irep->iseq);
     if (loc.lineno == -1) continue;
 
-    loc.filename = mrb_debug_get_filename(irep, pc - irep->iseq);
+    loc.filename = mrb_debug_get_filename(mrb, irep, pc - irep->iseq);
     if (!loc.filename) {
       loc.filename = "(unknown)";
     }
diff --git a/src/class.c b/src/class.c
index 3354617bb..5c5ee9d17 100644
--- a/src/class.c
+++ b/src/class.c
@@ -484,15 +484,11 @@ mrb_define_method(mrb_state *mrb, struct RClass *c, const char *name, mrb_func_t
 MRB_API void
 mrb_notimplement(mrb_state *mrb)
 {
-  const char *str;
-  mrb_int len;
   mrb_callinfo *ci = mrb->c->ci;
 
   if (ci->mid) {
-    str = mrb_sym2name_len(mrb, ci->mid, &len);
-    mrb_raisef(mrb, E_NOTIMP_ERROR,
-      "%S() function is unimplemented on this machine",
-      mrb_str_new_static(mrb, str, (size_t)len));
+    mrb_value str = mrb_sym2str(mrb, ci->mid);
+    mrb_raisef(mrb, E_NOTIMP_ERROR, "%S() function is unimplemented on this machine", str);
   }
 }
 
@@ -1686,11 +1682,7 @@ mrb_class_path(mrb_state *mrb, struct RClass *c)
   }
   else if (mrb_symbol_p(path)) {
     /* toplevel class/module */
-    const char *str;
-    mrb_int len;
-
-    str = mrb_sym2name_len(mrb, mrb_symbol(path), &len);
-    return mrb_str_new(mrb, str, len);
+    return mrb_sym2str(mrb, mrb_symbol(path));
   }
   return mrb_str_dup(mrb, path);
 }
diff --git a/src/codedump.c b/src/codedump.c
index c9c3b25ef..5bffefddb 100644
--- a/src/codedump.c
+++ b/src/codedump.c
@@ -48,11 +48,11 @@ print_lv_ab(mrb_state *mrb, mrb_irep *irep, uint16_t a, uint16_t b)
 }
 
 static void
-print_header(mrb_irep *irep, ptrdiff_t i)
+print_header(mrb_state *mrb, mrb_irep *irep, ptrdiff_t i)
 {
   int32_t line;
 
-  line = mrb_debug_get_line(irep, i);
+  line = mrb_debug_get_line(mrb, irep, i);
   if (line < 0) {
     printf("      ");
   }
@@ -99,12 +99,12 @@ codedump(mrb_state *mrb, mrb_irep *irep)
     ai = mrb_gc_arena_save(mrb);
 
     i = pc - irep->iseq;
-    next_file = mrb_debug_get_filename(irep, i);
+    next_file = mrb_debug_get_filename(mrb, irep, i);
     if (next_file && file != next_file) {
       printf("file: %s\n", next_file);
       file = next_file;
     }
-    print_header(irep, i);
+    print_header(mrb, irep, i);
     ins = READ_B();
     switch (ins) {
     CASE(OP_NOP, Z):
@@ -491,7 +491,7 @@ codedump(mrb_state *mrb, mrb_irep *irep)
     CASE(OP_EXT1, Z):
       ins = READ_B();
       printf("OP_EXT1\n");
-      print_header(irep, pc-irep->iseq-2);
+      print_header(mrb, irep, pc-irep->iseq-2);
       switch (ins) {
 #define OPCODE(i,x) case OP_ ## i: FETCH_ ## x ## _1 (); goto L_OP_ ## i;
 #include "mruby/ops.h"
@@ -501,7 +501,7 @@ codedump(mrb_state *mrb, mrb_irep *irep)
     CASE(OP_EXT2, Z):
       ins = READ_B();
       printf("OP_EXT2\n");
-      print_header(irep, pc-irep->iseq-2);
+      print_header(mrb, irep, pc-irep->iseq-2);
       switch (ins) {
 #define OPCODE(i,x) case OP_ ## i: FETCH_ ## x ## _2 (); goto L_OP_ ## i;
 #include "mruby/ops.h"
@@ -511,7 +511,7 @@ codedump(mrb_state *mrb, mrb_irep *irep)
     CASE(OP_EXT3, Z):
       ins = READ_B();
       printf("OP_EXT3\n");
-      print_header(irep, pc-irep->iseq-2);
+      print_header(mrb, irep, pc-irep->iseq-2);
       switch (ins) {
 #define OPCODE(i,x) case OP_ ## i: FETCH_ ## x ## _3 (); goto L_OP_ ## i;
 #include "mruby/ops.h"
diff --git a/src/debug.c b/src/debug.c
index 2949131e4..0dc02a1e3 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -51,20 +51,20 @@ select_line_type(const uint16_t *lines, size_t lines_len)
 }
 
 MRB_API char const*
-mrb_debug_get_filename(mrb_irep *irep, ptrdiff_t pc)
+mrb_debug_get_filename(mrb_state *mrb, mrb_irep *irep, ptrdiff_t pc)
 {
   if (irep && pc >= 0 && pc < irep->ilen) {
     mrb_irep_debug_info_file* f = NULL;
     if (!irep->debug_info) return NULL;
     else if ((f = get_file(irep->debug_info, (uint32_t)pc))) {
-      return f->filename;
+      return mrb_sym2name_len(mrb, f->filename_sym, NULL);
     }
   }
   return NULL;
 }
 
 MRB_API int32_t
-mrb_debug_get_line(mrb_irep *irep, ptrdiff_t pc)
+mrb_debug_get_line(mrb_state *mrb, mrb_irep *irep, ptrdiff_t pc)
 {
   if (irep && pc >= 0 && pc < irep->ilen) {
     mrb_irep_debug_info_file* f = NULL;
@@ -129,7 +129,6 @@ mrb_debug_info_append_file(mrb_state *mrb, mrb_irep_debug_info *d,
   mrb_irep_debug_info_file *f;
   uint32_t file_pc_count;
   size_t fn_len;
-  mrb_int len;
   uint32_t i;
 
   if (!d) return NULL;
@@ -138,8 +137,10 @@ mrb_debug_info_append_file(mrb_state *mrb, mrb_irep_debug_info *d,
   mrb_assert(filename);
   mrb_assert(lines);
 
-  if (d->flen > 0 && strcmp(filename, d->files[d->flen - 1]->filename) == 0) {
-    return NULL;
+  if (d->flen > 0) {
+    const char *fn = mrb_sym2name_len(mrb, d->files[d->flen - 1]->filename_sym, NULL);
+    if (strcmp(filename, fn) == 0)
+      return NULL;
   }
 
   f = (mrb_irep_debug_info_file*)mrb_malloc(mrb, sizeof(*f));
@@ -156,8 +157,6 @@ mrb_debug_info_append_file(mrb_state *mrb, mrb_irep_debug_info *d,
 
   fn_len = strlen(filename);
   f->filename_sym = mrb_intern(mrb, filename, fn_len);
-  len = 0;
-  f->filename = mrb_sym2name_len(mrb, f->filename_sym, &len);
 
   f->line_type = select_line_type(lines + start_pos, end_pos - start_pos);
   f->lines.ptr = NULL;
diff --git a/src/error.c b/src/error.c
index 50d1ab6f9..e69812dda 100644
--- a/src/error.c
+++ b/src/error.c
@@ -208,8 +208,8 @@ exc_debug_info(mrb_state *mrb, struct RObject *exc)
     if (err && ci->proc && !MRB_PROC_CFUNC_P(ci->proc)) {
       mrb_irep *irep = ci->proc->body.irep;
 
-      int32_t const line = mrb_debug_get_line(irep, err - irep->iseq);
-      char const* file = mrb_debug_get_filename(irep, err - irep->iseq);
+      int32_t const line = mrb_debug_get_line(mrb, irep, err - irep->iseq);
+      char const* file = mrb_debug_get_filename(mrb, irep, err - irep->iseq);
       if (line != -1 && file) {
         mrb_obj_iv_set(mrb, exc, mrb_intern_lit(mrb, "file"), mrb_str_new_cstr(mrb, file));
         mrb_obj_iv_set(mrb, exc, mrb_intern_lit(mrb, "line"), mrb_fixnum_value(line));
diff --git a/src/load.c b/src/load.c
index 55e0845f3..ab0346750 100644
--- a/src/load.c
+++ b/src/load.c
@@ -317,7 +317,6 @@ read_debug_record(mrb_state *mrb, const uint8_t *start, mrb_irep* irep, size_t *
   for (f_idx = 0; f_idx < irep->debug_info->flen; ++f_idx) {
     mrb_irep_debug_info_file *file;
     uint16_t filename_idx;
-    mrb_int len;
 
     file = (mrb_irep_debug_info_file *)mrb_malloc(mrb, sizeof(*file));
     irep->debug_info->files[f_idx] = file;
@@ -330,8 +329,6 @@ read_debug_record(mrb_state *mrb, const uint8_t *start, mrb_irep* irep, size_t *
     bin += sizeof(uint16_t);
     mrb_assert(filename_idx < filenames_len);
     file->filename_sym = filenames[filename_idx];
-    len = 0;
-    file->filename = mrb_sym2name_len(mrb, file->filename_sym, &len);
 
     file->line_entry_count = bin_to_uint32(bin);
     bin += sizeof(uint32_t);
diff --git a/src/symbol.c b/src/symbol.c
index 8ca03344c..96ca9dd17 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -520,7 +520,14 @@ mrb_sym2name(mrb_state *mrb, mrb_sym sym)
     return name;
   }
   else {
-    mrb_value str = mrb_str_dump(mrb, mrb_str_new_static(mrb, name, len));
+    mrb_value str;
+    if (sym&1) {                /* inline symbol */
+      str = mrb_str_new(mrb, name, len);
+    }
+    else {
+      str = mrb_str_new_static(mrb, name, len);
+    }
+    str = mrb_str_dump(mrb, str);
     return RSTRING_PTR(str);
   }
 }