[mtk: the coding style used in the example could lead people to
inject memory leaks in their code if they cut/paste/modify the
code to replace "exit" paths with "return" paths from a library
function.]
[Marko, from the mail thread discussing this patch:]
You are right about terminating the process. However, people copy
that example and put the code in a function changing "exit" to
"return". There are a bunch of examples like that here
https://beej.us/guide/bgnet/html/#poll, for instance. That error
bothered me when reading the network programming guide
https://beej.us/guide/bgnet/html/. Than I looked for information
elsewhere:
https://stackoverflow.com/questions/6712740/valgrind-reporting-that-getaddrinfo-is-leaking-memoryhttps://stackoverflow.com/questions/15690303/server-client-sockets-freeaddrinfo3-placement
And finally, I checked manual pages and saw where these errors
come from.
When you change that to a function and return without doing
freeaddrinfo, that is a memory leak. I believe an example should
show good programming practices. Relying on exiting and clearing
the memory in that case is not such a case. In my opinion, these
examples lead people to make mistakes in their programs.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Let's move to the 21st century. Instead of casting system data
types to long/long long/etc. in printf() calls, instead cast to
intmax_t or uintmax_t, the largest available signed/unsigned
integer types.
[mtk: rewrote commit message]
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Use printf()'s '#' flag character to prepend the string "0x".
However, when the number is printed in uppercase, and the prefix
is in lowercase, the string "0x" needs to be manually written.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
For consistency.
The types are written both with and without the redundant 'int' keyword
all over the man-pages. However, the most used form, by far, is the one
without 'int'.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Member 'tv_nsec' of 'struct timespec' is of type 'long' (see time.h.0p),
and therefore, the cast is completely redundant.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
For consistency.
Most man pages use 'long' instead of 'long int'.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
It is the DT_RUNPATH/DT_RPATH of the calling object (not the
executable) that is relevant for the library search. Verified
by experiment.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
fread(3), unlike read(2) which returns a ssize_t, returns a
size_t. It doesn't distinguish between error and enf-of-file.
Instead, either ferror(3) or feof(3) need to be checked if fread()
returned 0.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
`p1` (and `p2` too) is `const void *` and it comes from a
`const char **` (for legacy reasons, argv is not `const` but should be
treated as if it were). That means, the ultimate `char` is `const`:
"a pointer to a pointer to a const char".
Let's see what is going on before the fix first, and then the fix.
Before the fix:
`(char *const *)` (I removed the space on purpose) casts `p1` to be
"a pointer to a const pointer to a non-const char". That's clearly
not what it originally was.
Then we dereference, ending with a `char *const`, which is
"a const pointer to a non-const char". But given that the pointer value
is passed to a function, `const` doesn't make sense there, because the
function will already take a copy of it, so it is impossible to modify
the pointer itself.
The fix:
`(const char **)` The only thing that is const is the ultimate `char`,
which is the only thing that matters, because it is the only thing
strcmp(3) has access to (everything else, i.e. the pointers, are
copies).
Then, after the dereference we end up with `const char *`, the type of
argv (more or less, as previously noted), which is also the type of the
arguments to strcmp(3).
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Casting `const void *` to `struct mi *` should result in a warning if
done implicitly. The explicit cast was probably silencing that warning.
`const` can and should be kept.
Now, casting `const void *` to `const struct mi *` is done implicitly.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The type `sigset_t *` is implicitly casted to `void *`.
Explicitly casting can silence warnings when mistakes are made, so it's
better to remove those casts when possible.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Casting `void *` to `double (*cosine)(double)` is already done
implicitly.
I had doubts about this one, but `gcc -Wall -Wextra` didn't complain
about it.
Explicitly casting can silence warnings when mistakes are made, so it's
better to remove those casts when possible.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The type of `val` is `int **`, and it will work with tsearch()
anyway because of implicit cast from `void *`, so declaring it as an
`int **` simplifies the code.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Casting `int *` to `const void *` is already done implicitly.
Not only that, but the explicit cast to `void *` was slightly
misleading.
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Rather than:
sometype x;
for (x = ....; ...)
use
for (sometype x = ...; ...)
This brings the declaration and use closer together (thus aiding
readability) and also clearly indicates the scope of the loop
counter variable.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Rather than writing things such as:
struct sometype *x;
...
x = malloc(sizeof(*x));
let's use C99 style so that the type info is in the same line as
the allocation:
struct sometype *x = malloc(sizeof(*x));
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Use ``sizeof`` consistently through all the examples in the following
way:
- Use the name of the variable instead of its type as argument for
``sizeof``.
Rationale:
https://www.kernel.org/doc/html/v5.8/process/coding-style.html#allocating-memory
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Use ``sizeof`` consistently through all the examples in the following
way:
- Use the name of the variable instead of its type as argument for
``sizeof``.
Rationale:
https://www.kernel.org/doc/html/v5.8/process/coding-style.html#allocating-memory
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Use ``sizeof`` consistently through all the examples in the following
way:
- Use the name of the variable instead of its type as argument for
``sizeof``.
Rationale:
https://www.kernel.org/doc/html/v5.8/process/coding-style.html#allocating-memory
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Use ``sizeof`` consistently through all the examples in the following
way:
- Use the name of the variable instead of its type as argument for
``sizeof``.
Rationale:
https://www.kernel.org/doc/html/v5.8/process/coding-style.html#allocating-memory
Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Alejandro Colomar