gbdev/rgbds
1
0
Fork 0
mirror of https://github.com/gbdev/rgbds.git synced 2025-11-20 10:12:06 +00:00
Code Issues Packages Projects Releases Wiki Activity

Fix two bugs with RGBASM fixed-point math (#1388)

Browse Source 
- Fixed-point formulas are implemented using IEEE-754 floating-point
  internally, which could give infinity or NaN values whose conversion
  to fixed-point integer was platform-dependent.
- Formatting fixed-point $8000_0000 (INT32_MIN, -2147483648) was
  not putting the negative sign in front.
This commit is contained in:
Sylvie
2024-03-31 12:53:20 -04:00
committed by GitHub
parent 6b5248f15b
commit 9ab3446d1a
5 changed files with 36 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
src/asm/format.cpp
View File

@@ -4,6 +4,7 @@
#include <algorithm>
#include <inttypes.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@@ -153,11 +154,10 @@ void FormatSpec::appendNumber(std::string &str, uint32_t value) const {
char signChar = sign; // 0 or ' ' or '+'
if (useType == 'd' || useType == 'f') {
int32_t v = value;
if (v < 0 && v != INT32_MIN) {
if (int32_t v = value; v < 0) {
signChar = '-';
value = -v;
if (v != INT32_MIN)
value = -v;
}
}
@@ -194,16 +194,20 @@ void FormatSpec::appendNumber(std::string &str, uint32_t value) const {
useFracWidth = 255;
}
snprintf(
valueBuf, sizeof(valueBuf), "%.*f", (int)useFracWidth, value / fix_PrecisionFactor()
);
double fval = fabs(value / fix_PrecisionFactor());
snprintf(valueBuf, sizeof(valueBuf), "%.*f", (int)useFracWidth, fval);
} else if (useType == 'd') {
// Decimal numbers may be formatted with a '-' sign by `snprintf`, so `abs` prevents that,
// with a special case for `INT32_MIN` since `labs(INT32_MIN)` is UB. The sign will be
// printed later from `signChar`.
uint32_t uval = value != (uint32_t)INT32_MIN ? labs((int32_t)value) : value;
snprintf(valueBuf, sizeof(valueBuf), "%" PRIu32, uval);
} else {
char const *spec = useType == 'd' ? "%" PRId32
: useType == 'u' ? "%" PRIu32
char const *spec = useType == 'u' ? "%" PRIu32
: useType == 'X' ? "%" PRIX32
: useType == 'x' ? "%" PRIx32
: useType == 'o' ? "%" PRIo32
: "%" PRId32;
: "%" PRIu32;
snprintf(valueBuf, sizeof(valueBuf), spec, value);
}