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https://github.com/mruby/mruby
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dearblue
891e852286
The purpose is two-fold:
1. to be able to specify a pointer directly when user data is used
When using `mrb_protect()`, it is necessary to allocate objects by `mrb_obj_cptr()` function when using user data.
Adding `mrb_protect_raw()` will make it simpler to reimplement `mrbgems/mruby-error`.
2. to correctly unwind callinfo when an exception is raised from a C function defined as a method (the main topic)
If a method call is made directly under `mrb_protect()` and a C function is called, control is returned from `mrb_protect()` if an exception occurs there.
In this case, callinfo is not restored, so it is out of sync.
Moreover, returning to mruby VM (`mrb_vm_exec()` function) in this state will indicate `ci->pc` of C function which is equal to `NULL`, and subsequent `JUMP` will cause `SIGSEGV`.
Following is an example that actually causes `SIGSEGV`:
- `crash.c`
```c
#include <mruby.h>
#include <mruby/compile.h>
#include <mruby/error.h>
static mrb_value
level1_body(mrb_state *mrb, mrb_value self)
{
return mrb_funcall(mrb, self, "level2", 0);
}
static mrb_value
level1(mrb_state *mrb, mrb_value self)
{
return mrb_protect(mrb, level1_body, self, NULL);
}
static mrb_value
level2(mrb_state *mrb, mrb_value self)
{
mrb_raise(mrb, E_RUNTIME_ERROR, "error!");
return mrb_nil_value();
}
int
main(int argc, char *argv[])
{
mrb_state *mrb = mrb_open();
mrb_define_method(mrb, mrb->object_class, "level1", level1, MRB_ARGS_NONE());
mrb_define_method(mrb, mrb->object_class, "level2", level2, MRB_ARGS_NONE());
mrb_p(mrb, mrb_load_string(mrb, "p level1"));
mrb_close(mrb);
return 0;
}
```
- compile & run
```console
% `bin/mruby-config --cc --cflags --ldflags` crash.c `bin/mruby-config --libs`
% ./a.out
zsh: segmentation fault (core dumped) ./a.out
```
After applying this patch, it will print exception object and exit normally.
The `mrb_protect()`, `mrb_ensure()` and `mrb_rescue_exceptions()` in `mrbgems/mruby-error` have been rewritten using `mrb_protect_raw()`.
146 lines
4.0 KiB
C
146 lines
4.0 KiB
C
/**
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** @file mruby/error.h - Exception class
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**
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** See Copyright Notice in mruby.h
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*/
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#ifndef MRUBY_ERROR_H
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#define MRUBY_ERROR_H
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#include "common.h"
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/**
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* MRuby error handling.
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*/
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MRB_BEGIN_DECL
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struct RException {
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MRB_OBJECT_HEADER;
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struct iv_tbl *iv;
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};
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#define mrb_exc_ptr(v) ((struct RException*)mrb_ptr(v))
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MRB_API void mrb_sys_fail(mrb_state *mrb, const char *mesg);
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MRB_API mrb_value mrb_exc_new_str(mrb_state *mrb, struct RClass* c, mrb_value str);
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#define mrb_exc_new_lit(mrb, c, lit) mrb_exc_new_str(mrb, c, mrb_str_new_lit(mrb, lit))
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#define mrb_exc_new_str_lit(mrb, c, lit) mrb_exc_new_lit(mrb, c, lit)
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MRB_API mrb_value mrb_make_exception(mrb_state *mrb, mrb_int argc, const mrb_value *argv);
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MRB_API mrb_value mrb_exc_backtrace(mrb_state *mrb, mrb_value exc);
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MRB_API mrb_value mrb_get_backtrace(mrb_state *mrb);
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MRB_API mrb_noreturn void mrb_no_method_error(mrb_state *mrb, mrb_sym id, mrb_value args, const char *fmt, ...);
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/* declaration for `fail` method */
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MRB_API mrb_value mrb_f_raise(mrb_state*, mrb_value);
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#if defined(MRB_64BIT) || defined(MRB_USE_FLOAT32) || defined(MRB_NAN_BOXING) || defined(MRB_WORD_BOXING)
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struct RBreak {
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MRB_OBJECT_HEADER;
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const struct RProc *proc;
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mrb_value val;
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};
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#define mrb_break_value_get(brk) ((brk)->val)
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#define mrb_break_value_set(brk, v) ((brk)->val = v)
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#else
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struct RBreak {
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MRB_OBJECT_HEADER;
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const struct RProc *proc;
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union mrb_value_union value;
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};
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#define RBREAK_VALUE_TT_MASK ((1 << 8) - 1)
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static inline mrb_value
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mrb_break_value_get(struct RBreak *brk)
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{
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mrb_value val;
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val.value = brk->value;
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val.tt = (enum mrb_vtype)(brk->flags & RBREAK_VALUE_TT_MASK);
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return val;
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}
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static inline void
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mrb_break_value_set(struct RBreak *brk, mrb_value val)
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{
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brk->value = val.value;
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brk->flags &= ~RBREAK_VALUE_TT_MASK;
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brk->flags |= val.tt;
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}
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#endif /* MRB_64BIT || MRB_USE_FLOAT32 || MRB_NAN_BOXING || MRB_WORD_BOXING */
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#define mrb_break_proc_get(brk) ((brk)->proc)
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#define mrb_break_proc_set(brk, p) ((brk)->proc = p)
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#define RBREAK_TAG_FOREACH(f) \
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f(RBREAK_TAG_BREAK, 0) \
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f(RBREAK_TAG_BREAK_UPPER, 1) \
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f(RBREAK_TAG_BREAK_INTARGET, 2) \
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f(RBREAK_TAG_RETURN_BLOCK, 3) \
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f(RBREAK_TAG_RETURN, 4) \
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f(RBREAK_TAG_RETURN_TOPLEVEL, 5) \
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f(RBREAK_TAG_JUMP, 6) \
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f(RBREAK_TAG_STOP, 7)
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#define RBREAK_TAG_DEFINE(tag, i) tag = i,
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enum {
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RBREAK_TAG_FOREACH(RBREAK_TAG_DEFINE)
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};
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#undef RBREAK_TAG_DEFINE
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#define RBREAK_TAG_BIT 3
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#define RBREAK_TAG_BIT_OFF 8
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#define RBREAK_TAG_MASK (~(~UINT32_C(0) << RBREAK_TAG_BIT))
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static inline uint32_t
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mrb_break_tag_get(struct RBreak *brk)
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{
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return (brk->flags >> RBREAK_TAG_BIT_OFF) & RBREAK_TAG_MASK;
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}
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static inline void
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mrb_break_tag_set(struct RBreak *brk, uint32_t tag)
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{
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brk->flags &= ~(RBREAK_TAG_MASK << RBREAK_TAG_BIT_OFF);
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brk->flags |= (tag & RBREAK_TAG_MASK) << RBREAK_TAG_BIT_OFF;
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}
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/**
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* Protect
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*
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* Implemented in the mruby-error mrbgem
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*/
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MRB_API mrb_value mrb_protect(mrb_state *mrb, mrb_func_t body, mrb_value data, mrb_bool *state);
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/**
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* Ensure
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*
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* Implemented in the mruby-error mrbgem
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*/
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MRB_API mrb_value mrb_ensure(mrb_state *mrb, mrb_func_t body, mrb_value b_data,
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mrb_func_t ensure, mrb_value e_data);
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/**
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* Rescue
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*
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* Implemented in the mruby-error mrbgem
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*/
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MRB_API mrb_value mrb_rescue(mrb_state *mrb, mrb_func_t body, mrb_value b_data,
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mrb_func_t rescue, mrb_value r_data);
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/**
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* Rescue exception
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*
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* Implemented in the mruby-error mrbgem
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*/
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MRB_API mrb_value mrb_rescue_exceptions(mrb_state *mrb, mrb_func_t body, mrb_value b_data,
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mrb_func_t rescue, mrb_value r_data,
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mrb_int len, struct RClass **classes);
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typedef mrb_value mrb_protect_raw_func(mrb_state *mrb, void *userdata);
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/**
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* This API function behaves like `mrb_protect()`.
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* The advantage is that it avoids objectifying the user data.
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*/
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MRB_API mrb_value mrb_protect_raw(mrb_state *mrb, mrb_protect_raw_func *body, void *userdata, mrb_bool *error);
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MRB_END_DECL
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#endif /* MRUBY_ERROR_H */
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