Use curl_getenv in Curl_qlogdir

[dvdzhuang]

getenv isn't defined on all platforms, which prevents vquic from building. I specifically ran into this issue building on PlayStation.

[vszakats]

Would you mind posting more details about your environment/toolchain
and the build output?

[dvdzhuang]

Sure; this is a follow-up on this change: d31a842

Sony has its own version of clang and ld, and the PlayStation SDK derives from FreeBSD but with quirks. I'm building curl 8.14.1 with nghttp3 1.10.9, ngtcp2 1.12.90, and OpenSSL 3.5.0.

This is the output:

[1]  <source dir>/curl/lib/vquic/vquic.c:648:26: error: call to undeclared function 'getenv'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
[1]    648 |   const char *qlog_dir = getenv("QLOGDIR");
[1]        |                          ^
[1]  <source dir>/curl/lib/vquic/vquic.c:648:15: error: incompatible integer to pointer conversion initializing 'const char *' with an expression of type 'int' [-Wint-conversion]
[1]    648 |   const char *qlog_dir = getenv("QLOGDIR");
[1]        |               ^          ~~~~~~~~~~~~~~~~~
[1]  2 errors generated.

[bagder]

curl_getenv() returns an allocated string, so with just replacement this seems to introduce a memory leak?

[dvdzhuang]

Ah sorry; I hadn't realized. Changed to make qlog_dir not const and freed at the end 👍

[bagder]

Thanks!