openssl: gcc8 warning -Wstringop-truncation

[vszakats]

i686-w64-mingw32-gcc -I. -I../include -I"../../nghttp2/pkg/usr/local/include" -I"../../libssh2/include" -I"../../libssh2/win32" -I"../../openssl/include" -I"../../zlib/pkg/usr/local" -I"../../brotli/pkg/usr/local/include" -DCURL_STATICLIB -fno-ident -DCURL_DISABLE_SSL_AUTO_LOAD_CONFIG -fno-asynchronous-unwind-tables -DNGHTTP2_STATICLIB -g -O2 -Wall -W -fno-strict-aliasing -m32 -DBUILDING_LIBCURL -DCURL_WITH_MULTI_SSL -DUSE_NGHTTP2 -DUSE_LIBSSH2 -DHAVE_LIBSSH2_H -DUSE_OPENSSL -DHAVE_OPENSSL_ENGINE_H -DHAVE_OPENSSL_PKCS12_H -DHAVE_ENGINE_LOAD_BUILTIN_ENGINES -DOPENSSL_NO_KRB5 -DHAVE_OPENSSL_SRP -DUSE_TLS_SRP -DUSE_SCHANNEL -DHAVE_LIBZ -DHAVE_ZLIB_H -DHAVE_BROTLI -DUSE_WIN32_IDN -DWANT_IDN_PROTOTYPES -DUSE_WINDOWS_SSPI -DENABLE_IPV6 -D_WIN32_WINNT=0x0501 -DHAVE_LDAP_SSL -c vtls/openssl.c -o vtls/openssl.o
In function 'ossl_keylog_callback.part.2',
    inlined from 'ossl_keylog_callback':
vtls/openssl.c:256:5: warning: 'strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
     strncpy(buf, line, linelen);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~
vtls/openssl.c: In function 'ossl_keylog_callback':
vtls/openssl.c:247:22: note: length computed here
     size_t linelen = strlen(line);
                      ^~~~~~~~~~~~
In function 'ossl_keylog_callback.part.2',
    inlined from 'ossl_keylog_callback':
vtls/openssl.c:256:5: warning: 'strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
     strncpy(buf, line, linelen);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~
vtls/openssl.c: In function 'ossl_keylog_callback':
vtls/openssl.c:247:22: note: length computed here
     size_t linelen = strlen(line);
                      ^~~~~~~~~~~~

Can't spot what may be wrong with the code. Swapping strncpy() for memcpy() makes the warning disappear.

[jay]

Nothing is wrong with it but memcpy is fine so let's do that.