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Add fbounds-safety annotations for count.

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Reasoning:

The function `NextTableBitSize` is only called by `BuildHuffmanTable`
(src/utils/huffman_utils.c:196). In `BuildHuffmanTable`, `count` is
defined as a local array `int count[MAX_ALLOWED_CODE_LENGTH + 1]`
(line 93). This array decays to a pointer when passed to
`NextTableBitSize`. The maximum index accessed within `NextTableBitSize`
is `MAX_ALLOWED_CODE_LENGTH - 1` (line 75, inside a loop where `len`
starts <= `MAX_ALLOWED_CODE_LENGTH` and increments up to
`MAX_ALLOWED_CODE_LENGTH`).

Since the caller provides an array of size `MAX_ALLOWED_CODE_LENGTH + 1`
and the accesses are within bounds, the `count` parameter in
`NextTableBitSize` is annotated with
`WEBP_COUNTED_BY(MAX_ALLOWED_CODE_LENGTH + 1)`. This resolves the
compiler error.

Bug: 432511821
Change-Id: I29a55dd7f09c04aa3a2394996cf0e123d985fcd0
This commit is contained in:
Arman Hasanzadeh
2025-08-19 22:15:25 -07:00
parent f2061209d0
commit f66f1ee95c
1 changed files with 3 additions and 2 deletions
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5
src/utils/huffman_utils.c
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@@ -68,8 +68,9 @@ static WEBP_INLINE void ReplicateValue(HuffmanCode* table, int step, int end,
// Returns the table width of the next 2nd level table. count is the histogram
// of bit lengths for the remaining symbols, len is the code length of the next
// processed symbol
static WEBP_INLINE int NextTableBitSize(const int* const count, int len,
int root_bits) {
static WEBP_INLINE int NextTableBitSize(
const int* const WEBP_COUNTED_BY(MAX_ALLOWED_CODE_LENGTH + 1) count,
int len, int root_bits) {
int left = 1 << (len - root_bits);
while (len < MAX_ALLOWED_CODE_LENGTH) {
left -= count[len];