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| author | Marko Hrastovec <marko.hrastovec@gmail.com> | 2020-09-17 07:33:32 +0200 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2020-09-17 09:12:24 +0200 |
| commit | a23b00988ae023f18bd31f18ab2fd32230637ce2 (patch) | |
| tree | a7085bc3c2da850e86711c6142f1f1f6ebee99a0 | |
| parent | 966d17b1c5916b2804e61834c8349ab59cfcd94e (diff) | |
| download | man-pages-a23b00988ae023f18bd31f18ab2fd32230637ce2.tar.gz | |
freeaddrinfo.3: Fix memory leaks in freeaddrinfo() examples
[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-memory
https://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>
| -rw-r--r-- | man3/getaddrinfo.3 | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/man3/getaddrinfo.3 b/man3/getaddrinfo.3 index c9a4b3e432..4d383bea05 100644 --- a/man3/getaddrinfo.3 +++ b/man3/getaddrinfo.3 @@ -711,13 +711,13 @@ main(int argc, char *argv[]) close(sfd); } + freeaddrinfo(result); /* No longer needed */ + if (rp == NULL) { /* No address succeeded */ fprintf(stderr, "Could not bind\en"); exit(EXIT_FAILURE); } - freeaddrinfo(result); /* No longer needed */ - /* Read datagrams and echo them back to sender */ for (;;) { @@ -804,13 +804,13 @@ main(int argc, char *argv[]) close(sfd); } + freeaddrinfo(result); /* No longer needed */ + if (rp == NULL) { /* No address succeeded */ fprintf(stderr, "Could not connect\en"); exit(EXIT_FAILURE); } - freeaddrinfo(result); /* No longer needed */ - /* Send remaining command\-line arguments as separate datagrams, and read responses from server */ |