fix stack overflow in GIF decoder (issue #1935)#1941
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April 23, 2026 21:22
…othings#1936)): Prevent integer overflows when processing large 16-bit PNG images by validating allocation sizes with stbi__mad3sizes_valid before calling malloc in stbi__convert_format16, stbi__convert_16_to_8, and stbi__convert_8_to_16 add size-validations in stb_image.h fixes nothings#1936
…othings#1936)): Prevent integer overflows when processing large 16-bit PNG images by validating allocation sizes with stbi__mad3sizes_valid before calling malloc in stbi__convert_format16, stbi__convert_16_to_8, and stbi__convert_8_to_16 Fixes nothings#1936
…e the recursive stbi__out_gif_code() with an iterative loop that stores suffix bytes in a small fixed-size buffer and then emits them in reverse order. this prevents a stack overflow (issue nothings#1935)
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recursive
stbi__out_gif_code()can overflow the stack on deeplychained LZW codes (up to 4096). This happens easily on platforms with
small stacks like WebAssembly.
Fix: replaced the recursive traversal with an explicit loop that
walks the prefix chain and stores suffixes in a temporary
buffer[4096],then emits them in reverse order. No change to output or behavior.
Tested:
stack‑limited Linux (ulimit -s 128) without crashing.
tests/stb_image_testpasses without regressions.Closes #1935.