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Date: Sun, 11 Sep 2022 09:51:15 +0200
From: =?ISO-8859-1?Q?R=E9mi_Denis-Courmont?= <remi@remlab.net>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>,
 Michael Niedermayer <michael@niedermayer.cc>
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Subject: Re: [FFmpeg-devel] [PATCH 2/5] avcodec/dstdec: Check for overflow
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Hi,

Down-casting to a signed type (here, int16_t) is implementation-defined. And while normal compilers do the expected thing, with modulo-2^n complement, sanitizers tend to dislike it.

AFAIK, the clean solution is via an union whence you assign the uint16_t member, and then read the int16_t member. Fortunately, GCC and LLVM are able to optimise that construct back to a single sign-extension.

Br,
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