6e58c12752
This macros have several benefits over the standard functions:
- The type of the allocated object (not the pointer) is specified as an
argument, which improves readability:
- It is directly obvious what is the type of the object just by
reading the macro call.
- It allows grepping for all allocations of a given type.
This is admittedly similar to using sizeof() to get the size of the
object, but we'll see why this is better.
- In the case of reallocation macros, an extra check is performed to
make sure that the previous pointer was compatible with the allocated
type, which can avoid some mistakes.
- The cast is performed automatically, with a pointer type derived from
the type of the object. This is the best point of this macro, since
it does an automatic cast, where there's no chance of typos.
Usually, programmers have to decide whether to cast or not the result
of malloc(3). Casts usually hide warnings, so are to be avoided.
However, these functions already return a void *, so a cast doesn't
really add much danger. Moreover, a cast can even add warnings in
this exceptional case, if the type of the cast is different than the
type of the assigned pointer. Performing a manual cast is still not
perfect, since there are chances that a mistake will be done, and
even ignoring accidents, they clutter code, hurting readability.
And now we have a cast that is synced with sizeof.
- Whenever the type of the object changes, since we perform an explicit
cast to the old type, there will be a warning due to type mismatch in
the assignment, so we'll be able to see all lines that are affected
by such a change. This is especially important, since changing the
type of a variable and missing to update an allocation call far away
from the declaration is easy, and the consequences can be quite bad.
Cc: Valentin V. Bartenev <vbartenev@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
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| .github | ||
| contrib | ||
| doc | ||
| docs | ||
| etc | ||
| lib | ||
| libmisc | ||
| libsubid | ||
| man | ||
| po | ||
| src | ||
| tests | ||
| .gitignore | ||
| .travis.yml | ||
| acinclude.m4 | ||
| AUTHORS.md | ||
| autogen.sh | ||
| ChangeLog | ||
| configure.ac | ||
| COPYING | ||
| Makefile.am | ||
| NEWS | ||
| README | ||
| README.md | ||
| SECURITY.md | ||
| shadow.spec.in | ||
| TODO | ||
shadow-utils
Introduction
The shadow-utils package includes the necessary programs for converting UNIX password files to the shadow password format, plus programs for managing user and group accounts. The pwconv command converts passwords to the shadow password format. The pwunconv command unconverts shadow passwords and generates a passwd file (a standard UNIX password file). The pwck command checks the integrity of password and shadow files. The lastlog command prints out the last login times for all users. The useradd, userdel, and usermod commands are used for managing user accounts. The groupadd, groupdel, and groupmod commands are used for managing group accounts.
Sites
Contacts
There are several ways to contact us:
- the general discussion mailing list
- the #shadow IRC channel on libera.chat:
- irc://irc.libera.chat/shadow
Mailing archives
- the general discussion mailing list archive
- the commit mailing list archive, only used for historical purposes
Authors and maintainers
Authors and maintainers are listed in AUTHORS.md.