问题描述
我正在开发一种使用clang解析和类型检查代码的工具，并且我试图找出是否有一种方法可以从源代码中获取非标准clang属性。例如，我想用循环不变式注释循环或用[[not_null]]注释表达式。这可能吗？也许有些选项会说
这是一个具体的例子：
struct custom { };
int test() {
int x;
switch (1) {
case 1:
x = 1;
[[fallthrough]] ;
case 2:
x = 2;
break;
}
[[custom()]]
if (1) { return 1; } else { return 0; }
}
最终的AST如下：
`-FunctionDecl 0x55a9780ebba0 <line:2:1,line:14:1> line:2:5 test 'int ()'
`-CompoundStmt 0x55a9780ec060 <col:12,line:14:1>
|-DeclStmt 0x55a9780ebd08 <line:3:3,col:8>
| `-VarDecl 0x55a9780ebca0 <col:3,col:7> col:7 used x 'int'
|-SwitchStmt 0x55a9780ebd40 <line:4:3,line:11:3>
| |-IntegerLiteral 0x55a9780ebd20 <line:4:11> 'int' 1
| `-CompoundStmt 0x55a9780ebf40 <col:14,line:11:3>
| |-CaseStmt 0x55a9780ebda0 <line:5:3,line:6:9>
| | |-ConstantExpr 0x55a9780ebd80 <line:5:8> 'int' Int: 1
| | | `-IntegerLiteral 0x55a9780ebd60 <col:8> 'int' 1
| | `-BinaryOperator 0x55a9780ebe08 <line:6:5,col:9> 'int' lvalue '='
| | |-DeclRefExpr 0x55a9780ebdc8 <col:5> 'int' lvalue Var 0x55a9780ebca0 'x' 'int'
| | `-IntegerLiteral 0x55a9780ebde8 <col:9> 'int' 1
| |-AttributedStmt 0x55a9780ebe58 <line:7:5,col:21> <<<<<<<<<<<<<<<<<<<<<<<<<<< GOT Fallthrough
| | |-FallThroughAttr 0x55a9780ebe30 <col:7>
| | `-NullStmt 0x55a9780ebe28 <col:21>
| |-CaseStmt 0x55a9780ebeb0 <line:8:3,line:9:9>
| | |-ConstantExpr 0x55a9780ebe90 <line:8:8> 'int' Int: 2
| | | `-IntegerLiteral 0x55a9780ebe70 <col:8> 'int' 2
| | `-BinaryOperator 0x55a9780ebf18 <line:9:5,col:9> 'int' lvalue '='
| | |-DeclRefExpr 0x55a9780ebed8 <col:5> 'int' lvalue Var 0x55a9780ebca0 'x' 'int'
| | `-IntegerLiteral 0x55a9780ebef8 <col:9> 'int' 2
| `-BreakStmt 0x55a9780ebf38 <line:10:5>
`-IfStmt 0x55a9780ec038 <line:13:3,col:41> has_else <<<<<<<<<<<<<<<<<<<<<<<<<<< MISSING custom
|-ImplicitCastExpr 0x55a9780ebf90 <col:7> 'bool' <IntegralToBoolean>
| `-IntegerLiteral 0x55a9780ebf70 <col:7> 'int' 1
|-CompoundStmt 0x55a9780ebfd8 <col:10,col:22>
| `-ReturnStmt 0x55a9780ebfc8 <col:12,col:19>
| `-IntegerLiteral 0x55a9780ebfa8 <col:19> 'int' 1
`-CompoundStmt 0x55a9780ec020 <col:29,col:41>
`-ReturnStmt 0x55a9780ec010 <col:31,col:38>
`-IntegerLiteral 0x55a9780ebff0 <col:38> 'int' 0
解决方法
是的，有可能。 AFAIK有两种方法。
首先是将您的新定义添加到Clang中。您可以在tools/clang/include/clang/Basic/Attr.td中修改Clang源。然后Clang知道您的新属性。缺点可能是您需要每次更改都重新构建整个源代码。
第二个是使用可用属性annotate。例如[[clang::annotate("not_null")]]。我个人更喜欢这种方法的灵活性。
这是一个MWE，假设我想搜索具有自定义属性的函数decl：
#define MY_ATTR [[clang::annotate("my_attr")]]
...
// i want to extract this attribute
MY_ATTR void foo(...) { ... }
我可以实现以下访问者功能：
bool VisitFunctionDecl(FunctionDecl *D) {
if (D->hasAttrs()) {
for (auto attr : D->getAttrs()) {
std::string attr_name(attr->getSpelling());
std::string attr_annotate("annotate");
std::string attr_my("annotate(\"my_attr\")");
if (attr_name == attr_annotate) {
std::string SS; llvm::raw_string_ostream S(SS);
attr->printPretty(S,Policy);
std::string attr_string(S.str());
if (attr_string.find(attr_my) != std::string::npos) {
// found it! do stuff here!
// ...
}
}
}
}
return true;
}
我认为您可以轻松地使其适应循环注释。