AWS-LC usage typically follows a "live at head" model. Projects pin to whatever the current latest of AWS-LC is at the time of update, and regularly update it to pick up new changes.
While the AWS-LC repository may contain project-specific branches, e.g.
integrate-pq, those are not supported release branches and must not as
such. In rare cases, AWS-LC will temporarily maintain a short-lived branch on
behalf of a project. Most such branches are no longer updated, because the
corresponding project no longer needs them, and we do not create new ones to
replace the ones that are no longer updated.
AWS-LC currently supports the following build systems:
- CMake version 3.0 or later.
The development build system is CMake and the CMake build knows how to
automatically generate the intermediate files that AWS-LC needs. However,
outside of the CMake environment, these intermediates are generated and
checked into the AWS-LC source repository in generated-src. This avoids
incorporating projects needing to support Perl and Go in their build systems.
The script util/generate_build_files.py
expects to be run from the aws-lc directory. The generated build files will
be output to aws-lc/generated-src. If you don't use any of the supported
build systems then you should augment generate_build_files.py with support
for it.
The script will pregenerate the intermediate files (see BUILDING.md for details about which tools will need to be installed) and output helper files for that build system. It doesn't generate a complete build script, just file and test lists, which change often.
Periodically an engineer will update the AWS-LC revision, regenerate these files and check in the updated result.
AWS-LC does not present a lot of configurability in order to reduce the number of configurations that need to be tested. But there are a couple of #defines that you may wish to set:
OPENSSL_NO_ASM prevents the use of assembly code (although it's up to you to
ensure that the build system doesn't link it in if you wish to reduce binary
size). This will have a significant performance impact but can be useful if you
wish to use tools like
AddressSanitizer that
interact poorly with assembly code.
OPENSSL_SMALL removes some code that is especially large at some performance
cost.
You cannot link multiple versions of AWS-LC/BoringSSL or OpenSSL into a single binary without dealing with symbol conflicts. If you are statically linking multiple versions together, there's not a lot that can be done because C doesn't have a module system.
If you are using multiple versions in a single binary, in different shared
objects, ensure you build AWS-LC with -fvisibility=hidden and do not
export any symbols. This will prevent any collisions with other
verisons that may be included in other shared objects. Note that this requires
that all callers of AWS-LC APIs live in the same shared object as AWS-LC.
If you require that AWS-LC APIs be used across shared object boundaries,
continue to build with -fvisibility=hidden but define
BORINGSSL_SHARED_LIBRARY in both AWS-LC and consumers. AWS-LC's own
source files (but not consumers' source files) must also build with
BORINGSSL_IMPLEMENTATION defined. This will export AWS-LC's public symbols
in the resulting shared object while hiding private symbols. However note that,
as with a static link, this precludes dynamically linking with another version
of AWS-LC/BoringSSL or OpenSSL.