UpsilonNumworks/Upsilon
1
0
Fork 0
mirror of https://github.com/UpsilonNumworks/Upsilon.git synced 2026-01-18 16:27:34 +01:00
Code Issues Packages Projects Releases Wiki Activity

[python] Fix bug in Micropython when parsing const char * in

Browse Source 
float/double

This is fixed in Micropython project by commit b768cc6ca8ed6d7430b86dc7ccb9ee2391b3a251
This commit is contained in:
Émilie Feral
2018-10-02 14:00:31 +02:00
committed by LeaNumworks
parent 9a58f25646
commit e45e653619
1 changed files with 16 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
python/src/py/parsenum.c
View File

@@ -173,14 +173,20 @@ mp_obj_t mp_parse_num_decimal(const char *str, size_t len, bool allow_imag, bool
// DEC_VAL_MAX only needs to be rough and is used to retain precision while not overflowing
// SMALL_NORMAL_VAL is the smallest power of 10 that is still a normal float
// EXACT_POWER_OF_10 is the largest value of x so that 10^x can be stored exactly in a float
// Note: EXACT_POWER_OF_10 is at least floor(log_5(2^mantissa_length)). Indeed, 10^n = 2^n * 5^n
// so we only have to store the 5^n part in the mantissa (the 2^n part will go into the float's
// exponent).
#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
#define DEC_VAL_MAX 1e20F
#define SMALL_NORMAL_VAL (1e-37F)
#define SMALL_NORMAL_EXP (-37)
#define EXACT_POWER_OF_10 (9)
#elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
#define DEC_VAL_MAX 1e200
#define SMALL_NORMAL_VAL (1e-307)
#define SMALL_NORMAL_EXP (-307)
#define EXACT_POWER_OF_10 (22)
#endif
const char *top = str + len;
@@ -286,7 +292,16 @@ mp_obj_t mp_parse_num_decimal(const char *str, size_t len, bool allow_imag, bool
exp_val -= SMALL_NORMAL_EXP;
dec_val *= SMALL_NORMAL_VAL;
}
dec_val *= MICROPY_FLOAT_C_FUN(pow)(10, exp_val);
// At this point, we need to multiply the mantissa by its base 10 exponent. If possible,
// we would rather manipulate numbers that have an exact representation in IEEE754. It
// turns out small positive powers of 10 do, whereas small negative powers of 10 don't.
// So in that case, we'll yield a division of exact values rather than a multiplication
// of slightly erroneous values.
if (exp_val < 0 && exp_val > -EXACT_POWER_OF_10) {
dec_val /= MICROPY_FLOAT_C_FUN(pow)(10, -exp_val);
} else {
dec_val *= MICROPY_FLOAT_C_FUN(pow)(10, exp_val);
}
}
// negate value if needed