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Because the python environment may already be up and running by the time static initializers are run, specifically when gem5 is built as a library and loaded with dlopen, we can't rely on all of the objects declaring python initialization callbacks having been constructed by the time the code which would execute them runs. To address that problem, this change keeps track of whether the initialization has already happened when a callback is installed, and if so, runs the callback immediately. The original implementation also had users install callbacks by overriding a virtual function in the PythonInitFunc class, and then statically allocating an instance of that subclass so its constructor would be called at initialization time. Calling the function manually if initialization has already happened won't work in that case, because you can't call a virtual function from a constructor and get the behavior you'd want. Instead, this change makes the PythonInitFunc wrap the actual callback which is outside of the structure itself. Because the callback is not a virtual function of PythonInitFunc, we can call it in the constructor without issue. Also, the Callback type has to be a bare function pointer and not a std::function<...> because the argument it takes is a pybind11::module_ reference. Pybind11 sets the visibility of all of its code to hidden to improve binary size, but unfortunately that causes problems when accepting one as an argument in a publically accessible lambda in g++. clang doesn't raise a warning, but g++ does which breaks the build. We could potentially disable this warning, but accepting a function pointer instead works just as well, since captureless lambdas can be trivially converted into function pointers, and they don't seem to upset g++. Change-Id: I3fb321b577090df67c7be3be0e677c2c2055d446 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54325 Maintainer: Gabe Black <gabe.black@gmail.com> Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Tested-by: kokoro <noreply+kokoro@google.com>
This is the gem5 simulator. The main website can be found at http://www.gem5.org A good starting point is http://www.gem5.org/about, and for more information about building the simulator and getting started please see http://www.gem5.org/documentation and http://www.gem5.org/documentation/learning_gem5/introduction. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/documentation/general_docs/building for more details concerning the minimum versions of these tools. Once you have all dependencies resolved, type 'scons build/<CONFIG>/gem5.opt' where CONFIG is one of the options in build_opts like ARM, NULL, MIPS, POWER, SPARC, X86, Garnet_standalone, etc. This will build an optimized version of the gem5 binary (gem5.opt) with the the specified configuration. See http://www.gem5.org/documentation/general_docs/building for more details and options. The main source tree includes these subdirectories: - build_opts: pre-made default configurations for gem5 - build_tools: tools used internally by gem5's build process. - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - include: include files for use in other programs - site_scons: modular components of the build system - src: source code of the gem5 simulator - system: source for some optional system software for simulated systems - tests: regression tests - util: useful utility programs and files To run full-system simulations, you may need compiled system firmware, kernel binaries and one or more disk images, depending on gem5's configuration and what type of workload you're trying to run. Many of those resources can be downloaded from http://resources.gem5.org, and/or from the git repository here: https://gem5.googlesource.com/public/gem5-resources/ If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.