Skip to content

Fix sign-extension of 64-bit literals #213

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
laurenthuberdeau wants to merge 2 commits into
base: main
Choose a base branch
from
Open

Fix sign-extension of 64-bit literals #213

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
47daf49
Fix sign-extension of 64-bit literals
laurenthuberdeau Nov 11, 2025
9f1fdab
WIP
laurenthuberdeau Nov 11, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 3 additions & 2 deletions exe.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -132,8 +132,9 @@ void emit_i32_le(int n) {

void emit_i64_le(int n) {
emit_i32_le(n);
// Sign extend to 64 bits. Arithmetic shift by 31 gives -1 for negative numbers and 0 for positive numbers.
emit_i32_le(n >> 31);
// Sign extend to 64 bits. Because int is not guaranteed to be exactly 32
// bits, we check the 32th bit (sign bit) and fill with 0xff... if set.
emit_i32_le(TERNARY(n & 0x80000000, -1, 0));
}

#ifdef SUPPORT_64_BIT_LITERALS
Expand Down
24 changes: 19 additions & 5 deletions pnut.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1029,13 +1029,15 @@ void u64_mul_u32(int *x, int y) {
int m3 = (m1 & 0xffff) + (m2 & 0xffff); /* 0 .. 0x1fffe */
int hi = xhi * yhi + I32_LOGICAL_RSHIFT_16(m1) + I32_LOGICAL_RSHIFT_16(m2) + I32_LOGICAL_RSHIFT_16(m3); /* 0 .. 0xfffffffe */
x[0] = ((m3 & 0xffff) << 16) + (lo & 0xffff);
// FIXME: Does that work with sizeof(int) > 4?
x[1] = x[1] * y + hi;
}

// x = x + y
void u64_add_u32(int *x, int y) {
int lo = x[0] + y;
// Carry (using signed integers)
// FIXME: Does that work with sizeof(int) > 4?
x[1] += ((x[0] < 0) != (lo < 0));
x[0] = lo;
}
Expand All @@ -1046,7 +1048,7 @@ void u64_add_u32(int *x, int y) {
// store it as a regular integer. The sign bit is used to distinguish between
// large ints (positive) and regular ints (negative).
void u64_to_obj(int *x) {
if (x[0] >= 0 && x[1] == 0) { // "small int"
if ((x[0] & 0x80000000) == 0 && x[1] == 0) { // "small int"
val = -x[0];
} else {
val = alloc_obj(2);
Expand All @@ -1056,7 +1058,7 @@ void u64_to_obj(int *x) {
}

#define DIGIT_BYTE (val_32[0] % 256)
#define INIT_ACCUM_DIGIT() val_32[0] = 0; val_32[1] = 0;
#define INIT_ACCUM_DIGIT() val_32[0] = val_32[1] = 0;
#else
#define DIGIT_BYTE (-val % 256)
#define INIT_ACCUM_DIGIT() val = 0;
Expand All @@ -1075,17 +1077,29 @@ int accum_digit(int base) {
if (digit >= base) {
return 0; // character is not a digit in that base
} else {
int limit = MININT / base;
if (base == 10 && if_macro_mask && ((val < limit) || ((val == limit) && (digit > limit * base - MININT)))) {

#ifdef SUPPORT_64_BIT_LITERALS
int limit_hi = MININT / base;
int limit_lo = (MININT % base + base) % base; // make it positive
if (base == 10 && if_macro_mask
&& ((val_32[1] < limit_hi)
|| ((val_32[1] == limit_hi) && (val_32[0] < limit_lo))
|| ((val_32[1] == limit_hi) && (val_32[0] == limit_lo) && (digit > limit_lo)))) {
fatal_error("literal integer overflow");
}

#ifdef SUPPORT_64_BIT_LITERALS
u64_mul_u32(val_32, base);
u64_add_u32(val_32, digit);
#else
int limit = MININT / base;
if (base == 10 && if_macro_mask
&& ((val < limit) || ((val == limit) && (digit > limit * base - MININT)))) {
fatal_error("literal integer overflow");
}

val = val * base - digit;
#endif

get_ch();
return 1;
}
Expand Down
Loading