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Merge pull request #246 from pfalcon/exc_stack_entry

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vm: Introduce structure for exception stack entry, record entry type.
This commit is contained in:
Damien George 2014-01-31 15:51:20 -08:00
commit 532f2c30f6
2 changed files with 102 additions and 14 deletions
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45
py/vm.c
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@ -13,8 +13,22 @@
#include "bc0.h"
#include "bc.h"
// (value) stack grows down (to be compatible with native code when passing pointers to the stack), top element is pointed to
// exception stack grows up, top element is pointed to
// Value stack grows up (this makes it incompatible with native C stack, but
// makes sure that arguments to functions are in natural order arg1..argN
// (Python semantics mandates left-to-right evaluation order, including for
// function arguments). Stack pointer is pre-incremented and points at the
// 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;
#define DECODE_UINT do { unum = *ip++; if (unum > 127) { unum = ((unum & 0x3f) << 8) | (*ip++); } } while (0)
#define DECODE_ULABEL do { unum = (ip[0] | (ip[1] << 8)); ip += 2; } while (0)
@ -83,8 +97,8 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
nlr_buf_t nlr;
volatile machine_uint_t currently_in_except_block = 0; // 0 or 1, to detect nested exceptions
machine_uint_t exc_stack[8]; // on the exception stack we store (ip, sp | X) for each block, X = previous value of currently_in_except_block
machine_uint_t *volatile exc_sp = &exc_stack[0] - 1; // stack grows up, exc_sp points to top of stack
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
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
@ -318,9 +332,12 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
// matched against: POP_BLOCK or POP_EXCEPT (anything else?)
case MP_BC_SETUP_EXCEPT:
case MP_BC_SETUP_FINALLY:
DECODE_ULABEL; // except labels are always forward
*++exc_sp = (machine_uint_t)ip + unum;
*++exc_sp = (((machine_uint_t)sp) | currently_in_except_block);
++exc_sp;
exc_sp->opcode = op;
exc_sp->handler = ip + unum;
exc_sp->val_sp = (((machine_uint_t)sp) | currently_in_except_block);
currently_in_except_block = 0; // in a try block now
break;
@ -359,8 +376,8 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
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]);
currently_in_except_block = (exc_sp[0] & 1); // restore previous state
exc_sp -= 2; // pop back to previous exception handler
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
exc_sp--; // pop back to previous exception handler
break;
// matched against: SETUP_EXCEPT
@ -371,8 +388,8 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
assert(currently_in_except_block);
//sp = (mp_obj_t*)(*exc_sp--);
//exc_sp--; // discard ip
currently_in_except_block = (exc_sp[0] & 1); // restore previous state
exc_sp -= 2; // pop back to previous exception handler
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
exc_sp--; // pop back to previous exception handler
//sp -= 3; // pop 3 exception values
break;
@ -550,8 +567,8 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
// at the moment we are just raising the very last exception (the one that caused the nested exception)
// move up to previous exception handler
currently_in_except_block = (exc_sp[0] & 1); // restore previous state
exc_sp -= 2; // pop back to previous exception handler
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
exc_sp--; // pop back to previous exception handler
}
if (exc_sp >= &exc_stack[0]) {
@ -559,8 +576,8 @@ bool mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_ob
currently_in_except_block = 1;
// catch exception and pass to byte code
sp = (mp_obj_t*)(exc_sp[0] & (~((machine_uint_t)1)));
ip = (const byte*)(exc_sp[-1]);
sp = (mp_obj_t*)(exc_sp->val_sp & (~((machine_uint_t)1)));
ip = exc_sp->handler;
// push(traceback, exc-val, exc-type)
PUSH(mp_const_none);
PUSH(nlr.ret_val);

71
tests/basics/try-finally1.py Normal file
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@ -0,0 +1,71 @@
print("noexc-finally")
try:
print("try")
finally:
print("finally")
print("noexc-finally-finally")
try:
print("try1")
try:
print("try2")
finally:
print("finally2")
finally:
print("finally1")
print()
print("noexc-finally-func-finally")
def func2():
try:
print("try2")
finally:
print("finally2")
try:
print("try1")
func2()
finally:
print("finally1")
print()
print("exc-finally-except")
try:
print("try1")
try:
print("try2")
foo()
except:
print("except2")
finally:
print("finally1")
print()
print("exc-finally-except-filter")
try:
print("try1")
try:
print("try2")
foo()
except NameError:
print("except2")
finally:
print("finally1")
print()
print("exc-except-finally-finally")
try: # top-level catch-all except to not fail script
try:
print("try1")
try:
print("try2")
foo()
finally:
print("finally2")
finally:
print("finally1")
except:
print("catch-all except")
print()