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fix: violating strict aliasing rules in most areas in the new code.

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Yes, I am aware there are plenty of violations in `conf.c`, but I'll
likely fix/rewrite those when I will use it. Since there are some other
changes I think I'll want to make.
This commit is contained in:
Quinn
2025-09-04 11:13:07 +02:00
parent 0baa1ac9e8
commit 08ab721622
3 changed files with 85 additions and 56 deletions
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98
src/dat/nbt.c
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@@ -12,29 +12,52 @@
#define MAX_DEPTH 512
/* Extracts a big endian 16 bit integer from address `buf`, converts it to host byte size if needed and returns. */
static inline u16 buftoh16(const void *restrict buf) {
u16 i;
memcpy(&i, buf, sizeof(i));
return be16toh(i);
}
/* Extracts a big endian 32 bit integer from address `buf`, converts it to host byte size if needed and returns. */
static inline u32 buftoh32(const void *restrict buf) {
u32 i;
memcpy(&i, buf, sizeof(i));
return be32toh(i);
}
/* Extracts a big endian 64 bit integer from address `buf`, converts it to host byte size if needed and returns. */
static inline u64 buftoh64(const void *restrict buf) {
u64 i;
memcpy(&i, buf, sizeof(i));
return be64toh(i);
}
/* Processes the incoming array data in `buf`. Which contains `nmem` items of `size`.
* The data shall be converted to little-endian on little-endian systems
* Outputs the allocated data to `out`, returns where the next pointer would be. */
static const u8 *procarr(const u8 *restrict buf, i32 nmem, uint size, struct nbt_array *restrict *restrict out) {
size_t len = nmem * size;
*out = malloc(sizeof(struct nbt_array) + len);
if (!*out) return buf + len;
static const u8 *procarr(const u8 *restrict buf, i32 nmemb, uint size, struct nbt_array *restrict out) {
size_t len = nmemb * size;
*out = (struct nbt_array){
out->nmemb = nmemb,
out->dat = malloc(len),
};
if (!out->dat)
return buf + len;
memcpy((*out)->dat, buf, len);
(*out)->len = nmem;
memcpy(out->dat, buf, len);
buf += len;
/* Only include this code for little-endian systems. Since only they require this logic.
* Producing optimised code for other platforms. */
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
if (size == 1) return buf;
size_t i = 0;
while (i < len) {
// BUG: strict aliasing
i32 i = 0;
while (i < nmemb) {
switch (size) {
case 2: *(u16 *)((*out)->dat + i) = be16toh(*(u16 *)((*out)->dat + i)); break;
case 4: *(u32 *)((*out)->dat + i) = be32toh(*(u32 *)((*out)->dat + i)); break;
case 8: *(u64 *)((*out)->dat + i) = be64toh(*(u64 *)((*out)->dat + i)); break;
case 2: ((u16 *)out->dat)[i] = be16toh(((u16 *)out->dat)[i]); break;
case 4: ((u32 *)out->dat)[i] = be16toh(((u32 *)out->dat)[i]); break;
case 8: ((u64 *)out->dat)[i] = be16toh(((u64 *)out->dat)[i]); break;
default: __builtin_unreachable(); // this should be impossible
}
i += size;
@@ -44,12 +67,10 @@ static const u8 *procarr(const u8 *restrict buf, i32 nmem, uint size, struct nbt
}
/* calls `procarr` for the simple types available. */
static const u8 *proclist(const u8 *restrict buf, struct nbt_array *restrict *restrict out) {
static const u8 *proclist(const u8 *restrict buf, struct nbt_array *restrict out) {
uint size;
*out = NULL;
switch (*buf) {
switch (*(u8 *)buf) {
case NBT_I8: size = 1; break;
case NBT_I16: size = 2; break;
case NBT_I32: // fall through
@@ -60,7 +81,9 @@ static const u8 *proclist(const u8 *restrict buf, struct nbt_array *restrict *re
}
buf++;
i32 len = (i32)be32toh(*(u32 *)buf); // BUG: strict aliasing
i32 len;
memcpy(&len, buf, 4);
len = be32toh(len);
buf += 4;
return procarr(buf, len, size, out);
}
@@ -72,28 +95,27 @@ const u8 *nbt_proctag(const u8 *restrict buf, u16 slen, void *restrict out) {
i32 nmem;
uint size;
// BUG: strict aliasing
switch (*buf) {
case NBT_I8: *(u8 *)out = *ptr; return ptr + 1;
case NBT_I16: *(u16 *)out = be16toh(*(u16 *)ptr); return ptr + 2;
case NBT_I16: *(u16 *)out = buftoh16(ptr); return ptr + 2;
case NBT_I32: // fall through
case NBT_F32: *(u32 *)out = be16toh(*(u32 *)ptr); return ptr + 4;
case NBT_F32: *(u32 *)out = buftoh32(ptr); return ptr + 4;
case NBT_I64: // fall through
case NBT_F64: *(u64 *)out = be16toh(*(u64 *)ptr); return ptr + 8;
case NBT_F64: *(u64 *)out = buftoh64(ptr); return ptr + 8;
case NBT_STR: nmem = be16toh(*(u16 *)ptr), size = 1, ptr += 2; break;
case NBT_ARR_I8: nmem = be32toh(*(u32 *)ptr), size = 1, ptr += 4; break;
case NBT_ARR_I32: nmem = be32toh(*(u32 *)ptr), size = 4, ptr += 4; break;
case NBT_ARR_I64: nmem = be32toh(*(u32 *)ptr), size = 8, ptr += 4; break;
case NBT_STR: nmem = buftoh16(ptr), size = 1, ptr += 2; break;
case NBT_ARR_I8: nmem = buftoh32(ptr), size = 1, ptr += 4; break;
case NBT_ARR_I32: nmem = buftoh32(ptr), size = 4, ptr += 4; break;
case NBT_ARR_I64: nmem = buftoh32(ptr), size = 8, ptr += 4; break;
case NBT_LIST:
return proclist(ptr, (struct nbt_array **)out);
return proclist(ptr, (struct nbt_array *)out);
return tmp;
default: return NULL;
}
return procarr(ptr, nmem, size, (struct nbt_array **)out);
return procarr(ptr, nmem, size, (struct nbt_array *)out);
}
@@ -104,20 +126,19 @@ const u8 *nbt_proctag(const u8 *restrict buf, u16 slen, void *restrict out) {
static const u8 *nexttag_list(const u8 *restrict ptr, uint *restrict const dpt, i32 *restrict const lens, u8 *restrict const tags) {
const u8 *tag = ptr;
ptr++;
// BUG: strict aliasing
switch (*tag) {
case NBT_END: break;
case NBT_I8: ptr += (i32)be32toh(*(u32 *)ptr) * 1; break;
case NBT_I16: ptr += (i32)be32toh(*(u32 *)ptr) * 2; break;
case NBT_I8: ptr += (i32)buftoh32(ptr) * 1; break;
case NBT_I16: ptr += (i32)buftoh32(ptr) * 2; break;
case NBT_I32: // fall through
case NBT_F32: ptr += (i32)be32toh(*(u32 *)ptr) * 4; break;
case NBT_F32: ptr += (i32)buftoh32(ptr) * 4; break;
case NBT_I64: // fall through
case NBT_F64: ptr += (i32)be32toh(*(u32 *)ptr) * 8; break;
case NBT_F64: ptr += (i32)buftoh32(ptr) * 8; break;
default:
// TODO: handle out of bounds... Might not be required if we use flexible array member
(*dpt)++;
tags[*dpt] = *tag;
lens[*dpt] = (i32)be32toh(*(u32 *)ptr); // BUG: strict aliasing
lens[*dpt] = (i32)buftoh32(ptr);
break;
}
ptr += 4;
@@ -139,10 +160,9 @@ static const u8 *nexttag(const u8 *restrict tag, uint *restrict const dpt, i32 *
*dpt -= !lens[*dpt];
} else {
type = *tag;
ptr += be16toh(*(u16 *)(tag + 1)) + 3; // BUG: strict aliasing
ptr += buftoh16(tag + 1) + 3;
}
// BUG: strict aliasing
switch (type) {
case NBT_I8: ptr += 1; break;
case NBT_I16: ptr += 2; break;
@@ -151,10 +171,10 @@ static const u8 *nexttag(const u8 *restrict tag, uint *restrict const dpt, i32 *
case NBT_I64: // fall through
case NBT_F64: ptr += 8; break;
case NBT_ARR_I8: ptr += 4 + (i32)be32toh(*(u32 *)ptr) * 1; break;
case NBT_ARR_I32: ptr += 4 + (i32)be32toh(*(u32 *)ptr) * 4; break;
case NBT_ARR_I64: ptr += 4 + (i32)be32toh(*(u32 *)ptr) * 8; break;
case NBT_STR: ptr += 2 + (u16)be16toh(*(u16 *)ptr) * 1; break;
case NBT_ARR_I8: ptr += 4 + (i32)buftoh32(ptr) * 1; break;
case NBT_ARR_I32: ptr += 4 + (i32)buftoh32(ptr) * 4; break;
case NBT_ARR_I64: ptr += 4 + (i32)buftoh32(ptr) * 8; break;
case NBT_STR: ptr += 2 + (u16)buftoh16(ptr) * 1; break;
case NBT_END: (*dpt)--; break;
case NBT_COMPOUND: (*dpt)++; break;