Let's add a compile time safe API to select an SSL backend. This function needs to be called *before* curl_global_init(), and can be called only once. Side note: we do not explicitly test that it is called before curl_global_init(), but we do verify that it is not called multiple times (even implicitly). If SSL is used before the function was called, it will use whatever the CURL_SSL_BACKEND environment variable says (or default to the first available SSL backend), and if a subsequent call to curl_global_sslset() disagrees with the previous choice, it will fail with CURLSSLSET_TOO_LATE. The function also accepts an "avail" parameter to point to a (read-only) NULL-terminated list of available backends. This comes in real handy if an application wants to let the user choose between whatever SSL backends the currently available libcurl has to offer: simply call curl_global_sslset(-1, NULL, &avail); which will return CURLSSLSET_UNKNOWN_BACKEND and populate the avail variable to point to the relevant information to present to the user. Just like with the HTTP/2 push functions, we have to add the function declaration of curl_global_sslset() function to the header file *multi.h* because VMS and OS/400 require a stable order of functions declared in include/curl/*.h (where the header files are sorted alphabetically). This looks a bit funny, but it cannot be helped. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> |
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Include files for libcurl, external users.
They're all placed in the curl subdirectory here for better fit in any kind
of environment. You must include files from here using...
#include <curl/curl.h>
... style and point the compiler's include path to the directory holding the
curl subdirectory. It makes it more likely to survive future modifications.
NOTE FOR LIBCURL HACKERS
* If you check out from git on a non-configure platform, you must run the
appropriate buildconf* script to set up files before being able of compiling
the library.
* We cannot assume anything else but very basic compiler features being
present. While libcurl requires an ANSI C compiler to build, some of the
earlier ANSI compilers clearly can't deal with some preprocessor operators.
* Newlines must remain unix-style for older compilers' sake.
* Comments must be written in the old-style /* unnested C-fashion */
To figure out how to do good and portable checks for features, operating
systems or specific hardwarare, a very good resource is Bjorn Reese's
collection at http://predef.sf.net/