bug#43040: grep 3.4: memory leak

[Paul Eggert]

I don't see the extra memory consumption as necessarily being a bug, if grep is 
trading space (which is relatively cheap) for time (which is less so). Perhaps 
someone with some time to spare could look into that in more detail.

The excess CPU consumption is clearly problematic, though. I installed the 
attached patches, which on your example causes 'grep' to be 3x faster than grep 
3.3 was. I hope this addresses any practical performance problems uncovered by 
that artificial test case. The first patch is a bit of a hack but does the real 
work; the rest are merely cleanups or very minor performance improvements.

0001-Omit-duplicate-regexps.patch
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0002-Simplify-regex_compile.patch
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0003-Simplify-pattern_file_name.patch
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0004-Prefer-rawmemchr-to-memchr-when-it-s-easy.patch
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