+ <alg> is one of: aria, bf, blake2, camellia, cast, chacha,
+ cmac, des, dh, dsa, ecdh, ecdsa, idea, md4, mdc2, ocb,
+ poly1305, rc2, rc4, rmd160, scrypt, seed, siphash, sm2, sm3,
+ sm4 or whirlpool. The "ripemd" algorithm is deprecated and
+ if used is synonymous with rmd160.
+
+ -Dxxx, -Ixxx, -Wp, -lxxx, -Lxxx, -Wl, -rpath, -R, -framework, -static
+ These system specific options will be recognised and
+ passed through to the compiler to allow you to define
+ preprocessor symbols, specify additional libraries, library
+ directories or other compiler options. It might be worth
+ noting that some compilers generate code specifically for
+ processor the compiler currently executes on. This is not
+ necessarily what you might have in mind, since it might be
+ unsuitable for execution on other, typically older,
+ processor. Consult your compiler documentation.
+
+ Take note of the VAR=value documentation below and how
+ these flags interact with those variables.
+
+ -xxx, +xxx, /xxx
+ Additional options that are not otherwise recognised are
+ passed through as they are to the compiler as well.
+ Unix-style options beginning with a '-' or '+' and
+ Windows-style options beginning with a '/' are recognized.
+ Again, consult your compiler documentation.
+
+ If the option contains arguments separated by spaces,
+ then the URL-style notation %20 can be used for the space
+ character in order to avoid having to quote the option.
+ For example, -opt%20arg gets expanded to -opt arg.
+ In fact, any ASCII character can be encoded as %xx using its
+ hexadecimal encoding.
+
+ Take note of the VAR=value documentation below and how
+ these flags interact with those variables.
+
+ VAR=value
+ Assignment of environment variable for Configure. These
+ work just like normal environment variable assignments,
+ but are supported on all platforms and are confined to
+ the configuration scripts only. These assignments override
+ the corresponding value in the inherited environment, if
+ there is one.
+
+ The following variables are used as "make variables" and
+ can be used as an alternative to giving preprocessor,
+ compiler and linker options directly as configuration.
+ The following variables are supported:
+
+ AR The static library archiver.
+ ARFLAGS Flags for the static library archiver.
+ AS The assembler compiler.
+ ASFLAGS Flags for the assembler compiler.
+ CC The C compiler.
+ CFLAGS Flags for the C compiler.
+ CXX The C++ compiler.
+ CXXFLAGS Flags for the C++ compiler.
+ CPP The C/C++ preprocessor.
+ CPPFLAGS Flags for the C/C++ preprocessor.
+ CPPDEFINES List of CPP macro definitions, separated
+ by a platform specific character (':' or
+ space for Unix, ';' for Windows, ',' for
+ VMS). This can be used instead of using
+ -D (or what corresponds to that on your
+ compiler) in CPPFLAGS.
+ CPPINCLUDES List of CPP inclusion directories, separated
+ the same way as for CPPDEFINES. This can
+ be used instead of -I (or what corresponds
+ to that on your compiler) in CPPFLAGS.
+ HASHBANGPERL Perl invocation to be inserted after '#!'
+ in public perl scripts (only relevant on
+ Unix).
+ LD The program linker (not used on Unix, $(CC)
+ is used there).
+ LDFLAGS Flags for the shared library, DSO and
+ program linker.
+ LDLIBS Extra libraries to use when linking.
+ Takes the form of a space separated list
+ of library specifications on Unix and
+ Windows, and as a comma separated list of
+ libraries on VMS.
+ RANLIB The library archive indexer.
+ RC The Windows resource compiler.
+ RCFLAGS Flags for the Windows resource compiler.
+ RM The command to remove files and directories.
+
+ These cannot be mixed with compiling / linking flags given
+ on the command line. In other words, something like this
+ isn't permitted.
+
+ ./config -DFOO CPPFLAGS=-DBAR -DCOOKIE
+
+ Backward compatibility note:
+
+ To be compatible with older configuration scripts, the
+ environment variables are ignored if compiling / linking
+ flags are given on the command line, except for these:
+
+ AR, CC, CXX, CROSS_COMPILE, HASHBANGPERL, PERL, RANLIB, RC
+ and WINDRES
+
+ For example, the following command will not see -DBAR:
+
+ CPPFLAGS=-DBAR ./config -DCOOKIE
+
+ However, the following will see both set variables:
+
+ CC=gcc CROSS_COMPILE=x86_64-w64-mingw32- \
+ ./config -DCOOKIE
+
+ If CC is set, it is advisable to also set CXX to ensure
+ both C and C++ compilers are in the same "family". This
+ becomes relevant with 'enable-external-tests' and
+ 'enable-buildtest-c++'.
+
+ reconf
+ reconfigure
+ Reconfigure from earlier data. This fetches the previous
+ command line options and environment from data saved in
+ "configdata.pm", and runs the configuration process again,
+ using these options and environment.
+ Note: NO other option is permitted together with "reconf".
+ This means that you also MUST use "./Configure" (or
+ what corresponds to that on non-Unix platforms) directly
+ to invoke this option.
+ Note: The original configuration saves away values for ALL
+ environment variables that were used, and if they weren't
+ defined, they are still saved away with information that
+ they weren't originally defined. This information takes
+ precedence over environment variables that are defined
+ when reconfiguring.
+
+ Displaying configuration data
+ -----------------------------
+
+ The configuration script itself will say very little, and finishes by
+ creating "configdata.pm". This perl module can be loaded by other scripts
+ to find all the configuration data, and it can also be used as a script to
+ display all sorts of configuration data in a human readable form.
+
+ For more information, please do:
+
+ $ ./configdata.pm --help # Unix