mirror of https://github.com/mkerrisk/man-pages
26499b040c
Use ``sizeof`` consistently through all the examples in the
following way:
- When the result of ``sizeof`` is multiplied (or otherwise
modified), write ``sizeof`` in the first place.
Rationale:
``(sizeof(x) * INT_MAX * 2)`` doesn't overflow.
``(INT_MAX * 2 * sizeof(x))`` overflows, giving incorrect
results.
As a side effect, the parentheses of ``sizeof`` are not next to
the parentheses of the whole expression, and it is visually
easier to read.
Detailed rationale:
In C, successive multiplications are evaluated left to right (*),
and therefore here is what happens (assuming x86_64):
``(sizeof(x) * INT_MAX * 2)``:
1) sizeof(x) * INT_MAX (the type is the largest of both, which
is size_t (unsigned long; uint64_t)).
2) ANS * 2 (the type is again the largest: size_t)
``(INT_MAX * 2 * sizeof(x))``:
1) INT_MAX * 2 (the type is the largest of both, which is
int as both are int (int; int32_t), so the
result is already truncated as it doesn't fit
an int; at this point, the intermediate result
will be 2^32 - 2 (``INT_MAX - 1``) (if I did
the math right)).
2) ANS * 2 (the type is again the largest of both: size_t;
however, ANS was already incorrect, so the
result will be an incorrect size_t value)
(*): https://en.cppreference.com/w/c/language/operator_precedence
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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| man6 | ||
| man7 | ||
| man8 | ||
| scripts | ||
| CONTRIBUTING | ||
| Changes | ||
| Changes.old | ||
| Makefile | ||
| README | ||
| man-pages-5.09.Announce | ||
| man-pages-5.09.lsm | ||
README
This package contains Linux man pages for sections 1 through 8. Some more information is given in the 'man-pages-x.y.Announce' file. Homepage ======== For information about the Linux man-pages project, see http://www.kernel.org/doc/man-pages/index.html. Bug reports and contributing ============================ If you have corrections and additions to suggest, see http://www.kernel.org/doc/man-pages/contributing.html (Although there is a mirror of this repository on GitHub, please don't report issues via the GitHub issue tracker!) For further information on contributing, see the CONTRIBUTING file. Installing and uninstalling =========================== "make install" will copy these man pages to /usr/share/man/man[1-8]. To install to a path different from /usr, use "make install prefix=/install/path". "make remove" or "make uninstall" will remove any man page in this distribution from its destination. Use with caution, and remember to use "prefix" if desired, as with the "install" target. "make" or "make all" will perform "make uninstall" followed by "make install". Copyrights ========== See the 'man-pages-x.y.Announce' file.