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Merge pull request #358 from pfalcon/gen-exc-stack 

objgenerator: Implement exception handling for generators
This commit is contained in:
Damien George 2014-03-22 17:46:53 +00:00
parent 626f6b8133 48caa09a9d
commit 463997f638
4 changed files with 115 additions and 28 deletions
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12
py/bc.h
View File

@ -4,6 +4,16 @@ typedef enum {
MP_VM_RETURN_EXCEPTION,
} mp_vm_return_kind_t;
// Exception stack entry
typedef struct _mp_exc_stack {
const byte *handler;
// bit 0 is saved currently_in_except_block value
machine_uint_t val_sp;
// We might only have 2 interesting cases here: SETUP_EXCEPT & SETUP_FINALLY,
// consider storing it in bit 1 of val_sp. TODO: SETUP_WITH?
byte opcode;
} mp_exc_stack;
mp_vm_return_kind_t mp_execute_byte_code(const byte *code, const mp_obj_t *args, uint n_args, const mp_obj_t *args2, uint n_args2, uint n_state, mp_obj_t *ret);
mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_obj_t *fastn, mp_obj_t **sp_in_out);
mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_obj_t *fastn, mp_obj_t **sp_in_out, mp_exc_stack *exc_stack, mp_exc_stack **exc_sp_in_out, volatile mp_obj_t inject_exc);
void mp_byte_code_print(const byte *code, int len);

35
py/objgenerator.c
View File

@ -56,8 +56,10 @@ typedef struct _mp_obj_gen_instance_t {
const byte *code_info;
const byte *ip;
mp_obj_t *sp;
mp_exc_stack *exc_sp;
uint n_state;
mp_obj_t state[];
mp_obj_t state[0]; // Variable-length
mp_exc_stack exc_state[0]; // Variable-length
} mp_obj_gen_instance_t;
void gen_instance_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
@ -68,7 +70,7 @@ mp_obj_t gen_instance_getiter(mp_obj_t self_in) {
return self_in;
}
STATIC mp_obj_t gen_next_send(mp_obj_t self_in, mp_obj_t send_value) {
STATIC mp_obj_t gen_resume(mp_obj_t self_in, mp_obj_t send_value, mp_obj_t throw_value) {
mp_obj_gen_instance_t *self = self_in;
if (self->ip == 0) {
return mp_const_stop_iteration;
@ -80,7 +82,9 @@ STATIC mp_obj_t gen_next_send(mp_obj_t self_in, mp_obj_t send_value) {
} else {
*self->sp = send_value;
}
mp_vm_return_kind_t vm_return_kind = mp_execute_byte_code_2(self->code_info, &self->ip, &self->state[self->n_state - 1], &self->sp);
mp_vm_return_kind_t vm_return_kind = mp_execute_byte_code_2(self->code_info, &self->ip,
&self->state[self->n_state - 1], &self->sp, (mp_exc_stack*)(self->state + self->n_state),
&self->exc_sp, throw_value);
switch (vm_return_kind) {
case MP_VM_RETURN_NORMAL:
// Explicitly mark generator as completed. If we don't do this,
@ -100,19 +104,21 @@ STATIC mp_obj_t gen_next_send(mp_obj_t self_in, mp_obj_t send_value) {
return *self->sp;
case MP_VM_RETURN_EXCEPTION:
self->ip = 0;
nlr_jump(self->state[self->n_state - 1]);
default:
// TODO
assert(0);
return mp_const_none;
}
}
mp_obj_t gen_instance_iternext(mp_obj_t self_in) {
return gen_next_send(self_in, mp_const_none);
return gen_resume(self_in, mp_const_none, MP_OBJ_NULL);
}
STATIC mp_obj_t gen_instance_send(mp_obj_t self_in, mp_obj_t send_value) {
mp_obj_t ret = gen_next_send(self_in, send_value);
mp_obj_t ret = gen_resume(self_in, send_value, MP_OBJ_NULL);
if (ret == mp_const_stop_iteration) {
nlr_jump(mp_obj_new_exception(&mp_type_StopIteration));
} else {
@ -122,8 +128,21 @@ STATIC mp_obj_t gen_instance_send(mp_obj_t self_in, mp_obj_t send_value) {
STATIC MP_DEFINE_CONST_FUN_OBJ_2(gen_instance_send_obj, gen_instance_send);
STATIC mp_obj_t gen_instance_throw(uint n_args, const mp_obj_t *args) {
mp_obj_t ret = gen_resume(args[0], mp_const_none, n_args == 2 ? args[1] : args[2]);
if (ret == mp_const_stop_iteration) {
nlr_jump(mp_obj_new_exception(&mp_type_StopIteration));
} else {
return ret;
}
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(gen_instance_throw_obj, 2, 4, gen_instance_throw);
STATIC const mp_method_t gen_type_methods[] = {
{ "send", &gen_instance_send_obj },
{ "throw", &gen_instance_throw_obj },
{ NULL, NULL }, // end-of-list sentinel
};
@ -137,11 +156,13 @@ const mp_obj_type_t gen_instance_type = {
};
mp_obj_t mp_obj_new_gen_instance(const byte *bytecode, uint n_state, int n_args, const mp_obj_t *args) {
mp_obj_gen_instance_t *o = m_new_obj_var(mp_obj_gen_instance_t, mp_obj_t, n_state);
// TODO: 4 is hardcoded number from vm.c, calc exc stack size instead.
mp_obj_gen_instance_t *o = m_new_obj_var(mp_obj_gen_instance_t, byte, n_state * sizeof(mp_obj_t) + 4 * sizeof(mp_exc_stack));
o->base.type = &gen_instance_type;
o->code_info = bytecode;
o->ip = bytecode;
o->sp = &o->state[0] - 1; // sp points to top of stack, which starts off 1 below the state
o->exc_sp = (mp_exc_stack*)(o->state + n_state) - 1;
o->n_state = n_state;
// copy args to end of state array, in reverse (that's how mp_execute_byte_code_2 needs it)

43
py/vm.c
View File

@ -17,16 +17,6 @@
// top element.
// Exception stack also grows up, top element is also pointed at.
// Exception stack entry
typedef struct _mp_exc_stack {
const byte *handler;
// bit 0 is saved currently_in_except_block value
machine_uint_t val_sp;
// We might only have 2 interesting cases here: SETUP_EXCEPT & SETUP_FINALLY,
// consider storing it in bit 1 of val_sp. TODO: SETUP_WITH?
byte opcode;
} mp_exc_stack;
// Exception stack unwind reasons (WHY_* in CPython-speak)
// TODO perhaps compress this to RETURN=0, JUMP>0, with number of unwinds
// left to do encoded in the JUMP number
@ -89,8 +79,10 @@ mp_vm_return_kind_t mp_execute_byte_code(const byte *code, const mp_obj_t *args,
}
}
mp_exc_stack exc_stack[4];
mp_exc_stack *exc_sp = &exc_stack[0] - 1;
// execute the byte code
mp_vm_return_kind_t vm_return_kind = mp_execute_byte_code_2(code, &ip, &state[n_state - 1], &sp);
mp_vm_return_kind_t vm_return_kind = mp_execute_byte_code_2(code, &ip, &state[n_state - 1], &sp, exc_stack, &exc_sp, MP_OBJ_NULL);
switch (vm_return_kind) {
case MP_VM_RETURN_NORMAL:
@ -113,7 +105,10 @@ mp_vm_return_kind_t mp_execute_byte_code(const byte *code, const mp_obj_t *args,
// MP_VM_RETURN_NORMAL, sp valid, return value in *sp
// MP_VM_RETURN_YIELD, ip, sp valid, yielded value in *sp
// MP_VM_RETURN_EXCEPTION, exception in fastn[0]
mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_obj_t *fastn, mp_obj_t **sp_in_out) {
mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out,
mp_obj_t *fastn, mp_obj_t **sp_in_out,
mp_exc_stack *exc_stack, mp_exc_stack **exc_sp_in_out,
volatile mp_obj_t inject_exc) {
// careful: be sure to declare volatile any variables read in the exception handler (written is ok, I think)
const byte *ip = *ip_in_out;
@ -123,14 +118,21 @@ mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **i
mp_obj_t obj1, obj2;
nlr_buf_t nlr;
volatile machine_uint_t currently_in_except_block = 0; // 0 or 1, to detect nested exceptions
mp_exc_stack exc_stack[4];
mp_exc_stack *volatile exc_sp = &exc_stack[0] - 1; // stack grows up, exc_sp points to top of stack
volatile machine_uint_t currently_in_except_block = (int)*exc_sp_in_out & 1; // 0 or 1, to detect nested exceptions
mp_exc_stack *volatile exc_sp = (void*)((int)*exc_sp_in_out & ~1); // stack grows up, exc_sp points to top of stack
const byte *volatile save_ip = ip; // this is so we can access ip in the exception handler without making ip volatile (which means the compiler can't keep it in a register in the main loop)
// outer exception handling loop
for (;;) {
if (nlr_push(&nlr) == 0) {
// If we have exception to inject, now that we finish setting up
// execution context, raise it. This works as if RAISE_VARARGS
// bytecode was executed.
if (inject_exc != MP_OBJ_NULL) {
mp_obj_t t = inject_exc;
inject_exc = MP_OBJ_NULL;
nlr_jump(rt_make_raise_obj(t));
}
// loop to execute byte code
for (;;) {
dispatch_loop:
@ -434,7 +436,7 @@ unwind_jump:
// matched against: SETUP_EXCEPT, SETUP_FINALLY, SETUP_WITH
case MP_BC_POP_BLOCK:
// we are exiting an exception handler, so pop the last one of the exception-stack
assert(exc_sp >= &exc_stack[0]);
assert(exc_sp >= exc_stack);
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
exc_sp--; // pop back to previous exception handler
break;
@ -443,7 +445,7 @@ unwind_jump:
case MP_BC_POP_EXCEPT:
// TODO need to work out how blocks work etc
// pops block, checks it's an exception block, and restores the stack, saving the 3 exception values to local threadstate
assert(exc_sp >= &exc_stack[0]);
assert(exc_sp >= exc_stack);
assert(currently_in_except_block);
//sp = (mp_obj_t*)(*exc_sp--);
//exc_sp--; // discard ip
@ -592,7 +594,7 @@ unwind_return:
}
nlr_pop();
*sp_in_out = sp;
assert(exc_sp == &exc_stack[0] - 1);
assert(exc_sp == exc_stack - 1);
return MP_VM_RETURN_NORMAL;
case MP_BC_RAISE_VARARGS:
@ -605,6 +607,7 @@ unwind_return:
nlr_pop();
*ip_in_out = ip;
*sp_in_out = sp;
*exc_sp_in_out = (void*)((int)exc_sp | currently_in_except_block);
return MP_VM_RETURN_YIELD;
case MP_BC_IMPORT_NAME:
@ -654,7 +657,7 @@ unwind_return:
while (currently_in_except_block) {
// nested exception
assert(exc_sp >= &exc_stack[0]);
assert(exc_sp >= exc_stack);
// TODO make a proper message for nested exception
// at the moment we are just raising the very last exception (the one that caused the nested exception)
@ -664,7 +667,7 @@ unwind_return:
exc_sp--; // pop back to previous exception handler
}
if (exc_sp >= &exc_stack[0]) {
if (exc_sp >= exc_stack) {
// set flag to indicate that we are now handling an exception
currently_in_except_block = 1;

53
tests/basics/generator-exc.py Normal file
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@ -0,0 +1,53 @@
# Test proper handling of exceptions within generator across yield
def gen():
try:
yield 1
raise ValueError
except ValueError:
print("Caught")
yield 2
for i in gen():
print(i)
# Test throwing exceptions out of generator
def gen2():
yield 1
raise ValueError
yield 2
yield 3
g = gen2()
print(next(g))
try:
print(next(g))
except ValueError:
print("ValueError")
try:
print(next(g))
except StopIteration:
print("StopIteration")
# Test throwing exception into generator
def gen3():
yield 1
try:
yield 2
except ValueError:
print("ValueError received")
yield 3
yield 4
yield 5
g = gen3()
print(next(g))
print(next(g))
print("out of throw:", g.throw(ValueError))
print(next(g))
try:
print("out of throw2:", g.throw(ValueError))
except ValueError:
print("Boomerang ValueError caught")