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curl/docs/libcurl/curl_slist_append.3
Daniel Gustafsson 5cc3285574 docs: mention potential leak in curl_slist_append
When a non-empty list is appended to, and used as the returnvalue,
the list pointer can leak in case of an allocation failure in the
curl_slist_append() call. This is correctly handled in curl code
usage but we weren't explicitly pointing it out in the API call
documentation. Fix by extending the RETURNVALUE manpage section
and example code.

Closes #3424
Reported-by: dnivras on github
Reviewed-by: Daniel Stenberg <daniel@haxx.se>
2019-01-02 12:49:49 +01:00

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2.5 KiB
Groff

.\" **************************************************************************
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.TH curl_slist_append 3 "19 Jun 2003" "libcurl 7.10.4" "libcurl Manual"
.SH NAME
curl_slist_append - add a string to an slist
.SH SYNOPSIS
.B #include <curl/curl.h>
.sp
.BI "struct curl_slist *curl_slist_append(struct curl_slist *" list,
.BI "const char * "string ");"
.ad
.SH DESCRIPTION
\fIcurl_slist_append(3)\fP appends a string to a linked list of strings. The
existing \fBlist\fP should be passed as the first argument and the new list is
returned from this function. Pass in NULL in the \fBlist\fP argument to create
a new list. The specified \fBstring\fP has been appended when this function
returns. \fIcurl_slist_append(3)\fP copies the string.
The list should be freed again (after usage) with
\fIcurl_slist_free_all(3)\fP.
.SH RETURN VALUE
A null pointer is returned if anything went wrong, otherwise the new list
pointer is returned. To avoid overwriting an existing non-empty list on
failure, the new list should be returned to a temporary variable which can
be tested for NULL before updating the original list pointer.
.SH EXAMPLE
.nf
CURL *handle;
struct curl_slist *slist=NULL;
struct curl_slist *temp=NULL;
slist = curl_slist_append(slist, "pragma:");
if (slist == NULL)
return -1;
temp = curl_slist_append(slist, "Accept:")
if (temp == NULL) {
curl_slist_free_all(slist);
return -1;
}
slist = temp;
curl_easy_setopt(handle, CURLOPT_HTTPHEADER, slist);
curl_easy_perform(handle);
curl_slist_free_all(slist); /* free the list again */
.fi
.SH "SEE ALSO"
.BR curl_slist_free_all "(3), "