I tryed to use CONF_modules_load_file(NULL, NULL, CONF_MFLAGS_DEFAULT_SECTION|CONF_MFLAGS_IGNORE_MISSING_FILE)
and it work's fine:
$ src/curl --engine list
Build-time engines:
rsax
rdrand
dynamic
pkcs11 <--- this one is not build-in engine

I looked at OpenSSL sources and fount that OpenSSL_config(NULL) uses 
CONF_modules_load_file(NULL, NULL, CONF_MFLAGS_DEFAULT_SECTION|CONF_MFLAGS_IGNORE_MISSING_FILE)
so do not see any difference. Mon, 2 Jun 2014 13:01:10 +0200 (CEST) от Daniel Stenberg <daniel_at_haxx.se>:
>On Mon, 2 Jun 2014, Дмитрий Фалько wrote:
>
>Thanks for your feedback on this issue!
>
>> I try to add OpenSSL_config(NULL) in openssl backeend initialization code
>> and it work perfectly for on Ubuntu 12.04(x86_64) and armv5te(old OMAP). So
>> seems that "but the first seems to not work" is not correct.
>
>The text refers to the bug report 1208 and in there "drook" reports
>( https://sourceforge.net/p/curl/bugs/1208/#9c55 ):
>
>   I just got the same issue with openssl PHP extension, which I tried to fix
>   the same way; it appeared that calling OPENSSL_config() two times in two
>   different modules (though curl extension doesn't do it directly) leads to
>   openssl configuration error.
>
>... so even if this fixes your problem in the short term, there's an obvious
>risk that this will make other's use cases burn. The amount of users running
>curl and PHP at once is not insignificant.
>
>Hence the suggestion to instead use CONF_modules_load_file() with a NULL
>filename ( https://sourceforge.net/p/curl/bugs/1208/#f3e4 ) but I've not gotten
>any feedback on how that actually works. Any chance you can try that and see
>if you can get that to work for you?
>
>--
>
>  / daniel.haxx.se

Best Regards!

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