libclang：在AST中缺少一些语句？

我编写了一个测试程序（parse_ast.c）来解析ac源文件（tt.c）以查看libclang是如何工作的，输出结果是AST的层次结构：

这里是测试文件：

/* tt.c */                                    // line 1
#include <unistd.h>
#include <stdio.h>

typedef ssize_t (*write_fn_t)(int, const void *, size_t);

void indirect_write(write_fn_t write_fn) {    // line 7
    (*write_fn)(1, "indirect calln", 14);
}

void direct_write() {                         // line 11
    write(1, "direct calln", 12);            // line 12 mising in the ast?
}

int main() {                                  // line 15
    direct_write();
    indirect_write(write);                    // line 17 missing in the ast?

    return 0;
}

输出显示如下所示：

 ...
 ...
 inclusion directive at tt.c (2, 1) to (2, 20)
 inclusion directive at tt.c (3, 1) to (3, 19)
 TypedefDecl at tt.c (5, 1) to (5, 57)
 TypeRef at tt.c (5, 9) to (5, 16)
 ParmDecl at tt.c (5, 31) to (5, 35)
 ParmDecl at tt.c (5, 36) to (5, 49)
 ParmDecl at tt.c (5, 50) to (5, 56)
 FunctionDecl at tt.c (7, 1) to (9, 2)
 ParmDecl at tt.c (7, 21) to (7, 40)
  TypeRef at tt.c (7, 21) to (7, 31)
 CompoundStmt at tt.c (7, 42) to (9, 2)
  CallExpr at tt.c (8, 5) to (8, 42)
   UnexposedExpr at tt.c (8, 5) to (8, 16)
    ParenExpr at tt.c (8, 5) to (8, 16)
     UnaryOperator at tt.c (8, 6) to (8, 15)
      UnexposedExpr at tt.c (8, 7) to (8, 15)
       DeclRefExpr at tt.c (8, 7) to (8, 15)
   IntegerLiteral at tt.c (8, 17) to (8, 18)
   UnexposedExpr at tt.c (8, 20) to (8, 37)
    UnexposedExpr at tt.c (8, 20) to (8, 37)
     StringLiteral at tt.c (8, 20) to (8, 37)
   IntegerLiteral at tt.c (8, 39) to (8, 41)
 FunctionDecl at tt.c (11, 1) to (13, 2)
 CompoundStmt at tt.c (11, 21) to (13, 2)        <- XXX no line 12?
 FunctionDecl at tt.c (15, 1) to (20, 2)
 CompoundStmt at tt.c (15, 12) to (20, 2)
  CallExpr at tt.c (16, 5) to (16, 19)
   UnexposedExpr at tt.c (16, 5) to (16, 17)
    DeclRefExpr at tt.c (16, 5) to (16, 17)      <- XXX no line 17?
  ReturnStmt at tt.c (19, 5) to (19, 13)
   IntegerLiteral at tt.c (19, 12) to (19, 13)

我们可以看到这三个函数（第7行的direct_write /第11行的/ indirect_write /第15行的main）在那里，绝大多数语句都可以在AST中找到，但我找不到任何代表第12行中的语句的东西，第17行。有人知道原因吗？

我在debian 2.6.32 squeeze上，在clang 3.1和3.2上进行了测试（从源代码编译）。

这是程序parse_ast.c：

#include <stddef.h>
#include <stdio.h>
#include <clang-c/Index.h>

enum CXChildVisitResult visit_fn(CXCursor cr, CXCursor parent,
        CXClientData client_data) {

    unsigned depth;
    unsigned line, column, offset;
    enum CXCursorKind kind;
    CXSourceRange extent;
    CXSourceLocation start, end;
    CXString kind_spelling, filename;
    CXFile file;

    depth = (unsigned)client_data;

    // print cursor kind
    kind = clang_getCursorKind(cr);
    kind_spelling = clang_getCursorKindSpelling(kind);
    fprintf(stdout, "%*s%s at", depth, " ", clang_getCString(kind_spelling));
    clang_disposeString(kind_spelling);

    // get extent
    extent = clang_getCursorExtent(cr);
    start = clang_getRangeStart(extent);
    end = clang_getRangeEnd(extent);

    // print start position
    clang_getExpansionLocation(start, &file, &line, &column, &offset);
    filename = clang_getFileName(file);
    fprintf(stdout, " %s (%u, %u) to", clang_getCString(filename), line,
            column);
    clang_disposeString(filename);

    // print end position
    clang_getExpansionLocation(end, &file, &line, &column, &offset);
    fprintf(stdout, " (%u, %u)n", line, column);

    // recursive
    clang_visitChildren(cr, visit_fn, (CXClientData)(depth + 1));

    return CXChildVisit_Continue;

}

int main(int argc, const char * const *argv) {
    CXIndex Index = clang_createIndex(0, 0);
    CXTranslationUnit TU = clang_parseTranslationUnit(Index, NULL,
            argv, argc, 0, 0, CXTranslationUnit_DetailedPreprocessingRecord);

    clang_visitChildren(clang_getTranslationUnitCursor(TU),
            visit_fn, 0);
    clang_disposeTranslationUnit(TU);
    clang_disposeIndex(Index);

    return 0;
}

更新 ：

这个问题是由于缺少一个头文件stddef.h，它在libclang的邮件列表中得到了回复http://clang-developers.42468.n3.nabble.com/libclang-missing-some-statements-in-the-AST-td4029641 html的

---

检查由clang_parseTranslationUnit()生成的诊断 - 即使遇到错误，也会生成AST，但显然不能保证它有意义。

我发现注释掉#include行导致了编译错误，但是生成了类似于你的AST（具体而言，第17行丢失）。

用ssize_t替换size_t和ssize_t （作为int ）的#include行会导致关于write()的隐式声明的编译警告，但AST包含第17行。

因此，我认为诊断程序应该显示的头文件中存在问题。 诊断可以通过例如检索

for (unsigned I = 0, N = clang_getNumDiagnostics(TU); I != N; ++I) { 
    CXDiagnostic Diag = clang_getDiagnostic(TU, I);
    CXString String = clang_formatDiagnostic(Diag, clang_defaultDiagnosticDisplayOptions());
    fprintf(stderr, "%sn", clang_getCString(String));
    clang_disposeString(String);
}

---

我正在使用libclang来解析和优化c代码，但用你的代码解析c源文件，我不能在CompoundStmt中看到CXCursor_BinaryOperator

例如

void OCTS_C_TimerMiliseconds_reset_Timers(OCTS_outC_C_TimerMiliseconds_Timers *outC)
{
    outC->init = kcg_true;
    /* 1 */ OCTS_Sign_INT_reset_Math(&outC->_1_Context_1);
    /* 2 */ OCTS_Sign_INT_reset_Math(&outC->Context_2);
    /* 1 */ OCTS_FallingEdge_reset_Edge(&outC->Context_1);
} 

结果是：

FunctionDecl at s.cpp (10, 1) to (17, 2) OCTS_C_TimerMiliseconds_reset_Timers 
ParmDecl at s.cpp (11, 3) to (11, 44) outC 
 TypeRef at s.cpp (11, 3) to (11, 38) OCTS_outC_C_TimerMiliseconds_Timers 
CompoundStmt at s.cpp (12, 1) to (17, 2)  

链接地址: http://www.djcxy.com/p/94573.html

上一篇: libclang: missing some statements in the AST?

下一篇: Two different words for getters by reference vs getters by copy