320d0b493a
Performing computations on size_t variables that we feed to
xmalloc and friends can be dangerous, as an integer overflow
can cause us to allocate a much smaller chunk than we
realized.
We already have unsigned_add_overflows(), but let's add
unsigned_mult_overflows() to that. Furthermore, rather than
have each site manually check and die on overflow, we can
provide some helpers that will:
- promote the arguments to size_t, so that we know we are
doing our computation in the same size of integer that
will ultimately be fed to xmalloc
- check and die on overflow
- return the result so that computations can be done in
the parameter list of xmalloc.
These functions are a lot uglier to use than normal
arithmetic operators (you have to do "st_add(foo, bar)"
instead of "foo + bar"). To at least limit the damage, we
also provide multi-valued versions. So rather than:
st_add(st_add(a, b), st_add(c, d));
you can write:
st_add4(a, b, c, d);
This isn't nearly as elegant as a varargs function, but it's
a lot harder to get it wrong. You don't have to remember to
add a sentinel value at the end, and the compiler will
complain if you get the number of arguments wrong. This
patch adds only the numbered variants required to convert
the current code base; we can easily add more later if
needed.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Git - the stupid content tracker
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"git" can mean anything, depending on your mood.
- random three-letter combination that is pronounceable, and not
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- stupid. contemptible and despicable. simple. Take your pick from the
dictionary of slang.
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See Documentation/gittutorial.txt to get started, then see
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If git has been correctly installed, then the tutorial can also be
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