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CVS commit: src/usr.bin/gzip

Module Name:    src
Committed By:   kamil
Date:           Tue Jun 12 00:42:17 UTC 2018

Modified Files:
        src/usr.bin/gzip: gzip.c

Log Message:
Correct Undefined Behavior in gzip(1)

Unportable left shift reported with MKSANITIZER=yes USE_SANITIZER=undefined:

# progress -zf ./games.tgz  tar -xp -C "./" -f -
/public/src.git/usr.bin/gzip/gzip.c:2126:33: runtime error: left shift of 251 by 24 places cannot be represented in type 'int'
100% |****************************************************************************************************************| 44500 KiB  119.69 MiB/s    00:00 ETA

Refactor the following code into something that is more clear
and fix signed integer shift, by casting all buf[] elements to
(unsigned int):

unsigned char buf[8];
uint32_t usize;
else {
    usize = buf[4] | buf[5] << 8 |
            buf[6] << 16 | buf[7] << 24;

New version:

    usize = buf[4];
    usize |= (unsigned int)buf[5] << 8;
    usize |= (unsigned int)buf[6] << 16;
    usize |= (unsigned int)buf[7] << 24;

Only the "<< 24" part needs explicit cast, but for consistency make the
integer promotion explicit and clear to a code reader.

Sponsored by <The NetBSD Foundation>

To generate a diff of this commit:
cvs rdiff -u -r1.112 -r1.113 src/usr.bin/gzip/gzip.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

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