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A few words on sofort's tool-finding logic
==========================================
# the goals of sofort's tool-finding logic are:
- follow a clear, transparent, and consistent logic
- allow users to easily specify per-build preferences
- allow distros to easily and cleanly use site-wide settings
# three-way terminology:
- native machine: where make(1) will be running.
- host machine: where the package's program or libraries will execute.
- target machine: where code generated by the host package will execute.
! NOTE, however, that the host/target distinction is only relevant
when building a code-generating utility (e.g. a compiler), and that
the two are otherwise rather synonymous. Moreover, in practice it
is much more common to see configure scripts being invoked with a
--target=<machine> argument specifying the host, than with a
--host=<machine> argument.
# invocation and names of binary tools:
- agnostic names (ar, nm, objdump, ...)
- branded names (llvm-ar, llvm-nm, llvm-objdump, ...)
- machine-prefixed agnostic names (x86_64-nt64-midipix-ar, ...)
- machine-prefixed branded names (x86_64-linux-gnu-gcc-ar, ...)
- machine-specifying branded tools, as in
llvm-ar --target=x86_64-linux.
# cross-compilation: default search order:
- machine-prefixed agnostic tools
- machine-prefixed branded tools, starting with the prefix
most commonly associated with the selected compiler (that is,
``gcc'' when using gcc, and ``llvm'' when using clang)
- (machine-specifying) agnostic tools
- (machine-speficying) branded tools, starting once again with the
prefix most commonly associated with the selected compiler
# native builds: default search order:
- agnostic tools
- machine-prefixed agnostic tools
- machine-prefixed branded tools
- branded tools
# using an alternate search order:
- --toolchain=<prefix> (e.g. --toolchain=llvm) --> search for tools
that begin with <prefix> before searching for agnostic tools
# restricting which tools may be searched:
- --zealous --> only search for agnostic tools
- --zealous=<prefix> --> only search for <prefix>-branded tools
# per-tool overrides, by example of the ``ar'' tool:
- AR=ar --> set AR to $(command -v ar)
- AR=/path/to/ar --> set AR to the specified absolute path
# host generated config file and variable names:
- ccenv/host.mk
- AR, NM, OBJDUMP, ...
# native generated config file and variable names:
- ccenv/native.mk
- NATIVE_AR, NATIVE_NM, NATIVE_OBJDUMP, ...
# distro: site-wide preferences
- --ccenv=/path/to/site-specific/ccenv
- use the above to create ccenv as a symlink to
/path/to/site-specific/ccenv, and to accordingly
skip configure's tool-finding step.
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