LLVM Compiler Infrastructure - Pathogen Fork

This fork extends the functionality of libclang. It is currently based on LLVM 12.0.1.

This fork exists primarily to support Biohazrd via ClangSharp.Pathogen. The API is generally designed to simplify calling from C# and little-to-no effort has been put in to making the API consistent.

All functionality provided by this fork can be found in PathogenExtensions.cpp.

This fork also includes a (slightly modified) copy of libClangSharp, see clang/tools/libclang/libClangSharp for details.

The primary APIs provided by this fork are:

• pathogen_GetRecordLayout
  • Allows inspecting the memory and vtable layout of records (structs, classes, and unions.)
  • Exposes information provided by ASTRecordLayout and MicrosoftVTableContext/ItaniumVTableContext in an ABI-agnostic manner.
  • The information provided for record layouts is largely based on the behavior of the -fdump-record-layouts switch.
  • The information provided for vtable layouts is somewhat based on the bahvior of the -fdump-vtable-layouts switch, but the implementation of this switch for Itanium and Microsoft ABIs is basically completely separate (the information provided by each isn't even consistent.)
  • Biohazrd does not currently process records with multiple inheritance or virtual bases, so information in this department has never been fully utilized and may be lacking.
• pathogen_Location_isFromMainFile
  • A variant of clang_Location_isFromMainFile that uses SourceManager::isInMainFile instead of SourceManager::isWrittenInMainFile.
  • In particular this function will consider cursors created from a macro expansion in the main file to be in the main file.
• pathogen_getOperatorOverloadInfo
  • Provides information about operator overloads (and whether a given function is an operator overload.)
• pathogen_getArgPassingRestrictions
  • Returns whether the given type is able to be passed in registers for by-value arguments (or return values.)
  • Note that the underlying method for this function (RecordDecl::getArgPassingRestrictions) only cares about C++ restrictions, it does not consider size-related restrictions.
• pathogen_ComputeConstantValue
  • Tries to compute the constant value of an expression or a variable's initializer and returns the constant value.
• pathogen_EnumerateMacros
  • Enumerates macros from the preprocessor and provides information about them.
• pathogen_GetUuidAttrGuid
  • Gets the GUID used for a COM interface from a __declspec(uuid) attribute.
• pathogen_GetSpecializationKind
  • Gets the kind of specialization for a ClassTemplateSpecializationDecl.
• pathogen_InstantiateSpecializedClassTemplate
  • Initializes the specified specialized class template declaration.
• pathogen_InstantiateAllFullySpecializedClassTemplates
  • Instantiates all fully-specializaed class templates in the translation unit.
• pathogen_EnumerateAllSpecializedClassTemplates
  • Enumerates all specialized class templates in the translation unit.
• pathogen_getTypeSpellingWithPlaceholder
  • Similar to clang_getTypeSpelling, except it allows specifying the placeholder used to pretty-print the type. (Makes it easy to print a type like int [10] as int someParameterName[10].)
• pathogen_BeginEnumerateDeclarationsRaw / pathogen_EnumerateDeclarationsRawMoveNext
  • Enumerates child declarations from a declaration context without any filtering.
  • In particular, this is useful for enumerating the members of an implicitly-instantiated template specialization.
• pathogen_IsFunctionCallable / pathogen_IsFunctionTypeCallable
  • Performs checks similar to what Clang does internally to determine if the required types are complete in order to call a function.
  • As a side-effect, will implicitly instantiate any templates required to perform the call.
  • nullptr is returned when the function is callable. Otherwise a set of one or more strings describing why the function cannot be called is returned.
  • Due to an unavoidable side-effect of how these functions work, unecessary informational diagnostics may be attached to the translation unit.
  • (This is because the diagnostics for an incomplete type involved in a function call are split between two areas within Clang. We can handle the error half but not the informational half.)
• pathogen_GetArrangedFunction
  • Queries Clang's code generator to determine how a function call is arranged.

This fork was never really intended to be merged into libclang proper. The API shape doesn't match exactly what libclang provides, and it only exists to support ClangSharp.Pathogen (and as such are accessed via C# bindings, hence the lack of a header file.)

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The LLVM Compiler Infrastructure

This directory and its sub-directories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

The README briefly describes how to get started with building LLVM. For more information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.

Getting Started with the LLVM System

Taken from https://llvm.org/docs/GettingStarted.html.

Overview

Welcome to the LLVM project!

The LLVM project has multiple components. The core of the project is itself called "LLVM". This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer. It also contains basic regression tests.

C-like languages use the Clang front end. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

Other components include: the libc++ C++ standard library, the LLD linker, and more.

Getting the Source Code and Building LLVM

The LLVM Getting Started documentation may be out of date. The Clang Getting Started page might have more accurate information.

This is an example work-flow and configuration to get and build the LLVM source:

1. Checkout LLVM (including related sub-projects like Clang):

   • git clone https://github.com/llvm/llvm-project.git

   • Or, on windows, git clone --config core.autocrlf=false https://github.com/llvm/llvm-project.git

2. Configure and build LLVM and Clang:

   • cd llvm-project

   • cmake -S llvm -B build -G <generator> [options]

     Some common build system generators are:

     • Ninja --- for generating Ninja build files. Most llvm developers use Ninja.
     • Unix Makefiles --- for generating make-compatible parallel makefiles.
     • Visual Studio --- for generating Visual Studio projects and solutions.
     • Xcode --- for generating Xcode projects.

     Some common options:

     • -DLLVM_ENABLE_PROJECTS='...' and -DLLVM_ENABLE_RUNTIMES='...' --- semicolon-separated list of the LLVM sub-projects and runtimes you'd like to additionally build. LLVM_ENABLE_PROJECTS can include any of: clang, clang-tools-extra, cross-project-tests, flang, libc, libclc, lld, lldb, mlir, openmp, polly, or pstl. LLVM_ENABLE_RUNTIMES can include any of libcxx, libcxxabi, libunwind, compiler-rt, libc or openmp. Some runtime projects can be specified either in LLVM_ENABLE_PROJECTS or in LLVM_ENABLE_RUNTIMES.

       For example, to build LLVM, Clang, libcxx, and libcxxabi, use -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi".

     • -DCMAKE_INSTALL_PREFIX=directory --- Specify for directory the full path name of where you want the LLVM tools and libraries to be installed (default /usr/local). Be careful if you install runtime libraries: if your system uses those provided by LLVM (like libc++ or libc++abi), you must not overwrite your system's copy of those libraries, since that could render your system unusable. In general, using something like /usr is not advised, but /usr/local is fine.

     • -DCMAKE_BUILD_TYPE=type --- Valid options for type are Debug, Release, RelWithDebInfo, and MinSizeRel. Default is Debug.

     • -DLLVM_ENABLE_ASSERTIONS=On --- Compile with assertion checks enabled (default is Yes for Debug builds, No for all other build types).

   • cmake --build build [-- [options] <target>] or your build system specified above directly.

     • The default target (i.e. ninja or make) will build all of LLVM.

     • The check-all target (i.e. ninja check-all) will run the regression tests to ensure everything is in working order.

     • CMake will generate targets for each tool and library, and most LLVM sub-projects generate their own check-<project> target.

     • Running a serial build will be slow. To improve speed, try running a parallel build. That's done by default in Ninja; for make, use the option -j NNN, where NNN is the number of parallel jobs, e.g. the number of CPUs you have.

   • For more information see CMake

Consult the Getting Started with LLVM page for detailed information on configuring and compiling LLVM. You can visit Directory Layout to learn about the layout of the source code tree.