llvm学习日记五：使用libclang了解clang AST

参考书：《Getting Started with LLVM Core Libraries》

抽象语法树的概念就不介绍了，网上介绍太多。

一、makefile

路径还是根据自己电脑更改。

LLVM_CONFIG ?= /Users/qinyao/LLVM/LLVM-9.0.0/build-release/bin/llvm-config

# CXX = /Users/qinyao/LLVM/LLVM-9.0.0/build-release/bin/clang++
CXXINCLUDE+=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1
# CXXINCLUDE+=/Users/qinyao/LLVM/LLVM-9.0.0/build-release/include/c++/v1
ISYSROOT+=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
LIB+=/Users/qinyao/LLVM/LLVM-9.0.0/build-release/lib

ifndef VERBOSE
QUIET:=@
endif

SRC_DIR?=$(PWD)
LDFLAGS+=$(shell $(LLVM_CONFIG) --ldflags)
COMMON_FLAGS=-Wall -Wextra -I$(CXXINCLUDE) -isysroot $(ISYSROOT) 
CXXFLAGS+=$(COMMON_FLAGS) $(shell $(LLVM_CONFIG) --cxxflags)
CPPFLAGS+=$(shell $(LLVM_CONFIG) --cppflags) -I$(SRC_DIR) 

CLANGLIBS = \
    -Wl\
    -lclang\
    -lclangFrontend\
    -lclangDriver\
    -lclangSerialization\
    -lclangParse\
    -lclangSema\
    -lclangAnalysis\
    -lclangEdit\
    -lclangAST\
    -lclangLex\
    -lclangBasic

LLVMLIBS=$(shell $(LLVM_CONFIG) --libs)
PROJECT=uselibclang
PROJECT_OBJECTS=uselibclang.o
default: $(PROJECT)


%.o : $(SRC_DIR)/%.cpp
    @echo Compiling $*.cpp
    $(QUIET)$(CXX) -c $(CPPFLAGS) $(CXXFLAGS) $< -I/Users/qinyao/LLVM/LLVM-9.0.0/llvm-9.0.0.src/tools/clang/include 
    
$(PROJECT) : $(PROJECT_OBJECTS)
    @echo Linking $@
    $(QUIET)$(CXX) -o $@ $(CXXFLAGS) $(LDFLAGS) $^ $(CLANGLIBS) $(LLVMLIBS) `$(LLVM_CONFIG) --system-libs`

clean::
    $(QUIET)rm -f $(PROJECT) $(PROJECT_OBJECTS)

二、cpp代码

• clang_visitChildren 最重要的函数，使用回调函数visitNode 遍历所有子节点,打印c函数名

extern "C" {
#include "clang-c/Index.h"
}
#include "llvm/Support/CommandLine.h"
#include <iostream>
using namespace llvm;
static cl::opt<std::string> FileName(cl::Positional, cl::desc("Input file"), cl::Required);

enum CXChildVisitResult visitNode (CXCursor cursor, CXCursor parent, CXClientData client_data) {
    
    if (clang_getCursorKind(cursor) == CXCursor_CXXMethod || clang_getCursorKind(cursor) == CXCursor_FunctionDecl) {
        CXString name = clang_getCursorSpelling(cursor);
        CXSourceLocation loc = clang_getCursorLocation(cursor);
        CXString fName;
        unsigned line = 0, col = 0;
        clang_getPresumedLocation(loc, &fName, &line, &col);
        std::cout << clang_getCString(fName) << ":"
        << line << ":"<< col << " declares "
        << clang_getCString(name) << std::endl;
        return CXChildVisit_Continue;
        }
    return CXChildVisit_Recurse;
}
        
int main(int argc, char** argv)
{
    cl::ParseCommandLineOptions(argc, argv, "AST Traversal Example");
    CXIndex index = clang_createIndex(0, 0);
    const char *args[] = {"-I/usr/include","-I." };
    CXTranslationUnit translationUnit = clang_parseTranslationUnit(index, FileName.c_str(), args, 2, NULL, 0,CXTranslationUnit_None);
    CXCursor cur = clang_getTranslationUnitCursor(translationUnit);
    clang_visitChildren(cur, visitNode, NULL);
    clang_disposeTranslationUnit(translationUnit);
    clang_disposeIndex(index);
    return 0;
    
}

三、编译执行

• 代码比较简单 hello.c

#include <stdio.h>
int main() {
    printf("hello, world!");
}

image.png