[cfe-dev] [llvm-dev] Looking for help with an ast matcher

[Mads Ravn via cfe-dev]

Hi Piotr,

Thanks. Yeah, it seemed a little weird, but it was what got me closest. I
found out that the matcher I supplied here was working for clang-query
3.8.1. I'm working on a clang-tidy module for 4.0.0 - it's not working
there.

Could you elaborate on the "onImplicitObjectArgument"? There is no document
on it on the clang page. So I wouldn't know how it works or what it does.

Best regards,
Mads Ravn

On Mon, Nov 28, 2016 at 10:50 PM Piotr Padlewski <piotr.padlewski at gmail.com>
wrote:

> Hi Mads,
> I formatted your matcher a little bit just to understand it:
>
> ifStmt(hasCondition(implicitCastExpr(hasImplicitDestinationType(
> isInteger()),
>                     has(cxxMemberCallExpr(callee(cxxMethodDecl(hasName("
> compare"))),
>                                           hasArgument(0,
> declRefExpr().bind("str2")),
>                                           callee(memberExpr(has(
> declRefExpr().bind("str1"))))))))).bind("case1")
>
> And this is the AST part that we care about
> |-IfStmt 0x7fba9625f5e8 <line:8:5, line:10:5>
>   | |-<<<NULL>>>
>   | |-<<<NULL>>>
>   | |-ImplicitCastExpr 0x7fba96258a80 <line:8:8, col:25> '_Bool'
> <IntegralToBoolean>
>   | | `-CXXMemberCallExpr 0x7fba96258a20 <col:8, col:25> 'int'
>   | |   |-MemberExpr 0x7fba962589e8 <col:8, col:13> '<bound member
> function type>' .compare 0x7fba956ba078
>   | |   | `-ImplicitCastExpr 0x7fba96258a50 <col:8> 'const class
> std::__1::basic_string<char>' lvalue <NoOp>
>   | |   |   `-DeclRefExpr 0x7fba962588e0 <col:8> 'std::string':'class
> std::__1::basic_string<char>' lvalue Var 0x7fba962585b8 'str1'
> 'std::string':'class std::__1::basic_string<char>'
>   | |   `-ImplicitCastExpr 0x7fba96258a68 <col:21> 'const class
> std::__1::basic_string<char>' lvalue <NoOp>
>   | |     `-DeclRefExpr 0x7fba962589b0 <col:21> 'std::string':'class
> std::__1::basic_string<char>' lvalue Var 0x7fba96258770 'str2'
> 'std::string':'class std::__1::basic_string<char>'
>
>
> The callee called twice seems weird. Try to replace second one with
> "onImplicitObjectArgument", or "on", or in the worst case - "has" (which
> would not be totally valid).
>
>
> Piotr.
>
> 2016-11-28 <20%2016%2011%2028> 9:06 GMT+01:00 Mads Ravn <
> madsravn at gmail.com>:
>
> Hi Piotr,
>
> I think I found a working matcher: match
> ifStmt(hasCondition(implicitCastExpr(hasImplicitDestinationType(isInteger()),
> has(cxxMemberCallExpr(callee(cxxMethodDecl(hasName("compare"))),
> hasArgument(0, declRefExpr().bind("str2")),
> callee(memberExpr(has(declRefExpr().bind("str1"))))))))).bind("case1")
>
> This one bind to both str1 and str2 in str1.compare(str2). I have included
> a code segment below. I have attached a screenshot of this matcher working
> from clang-query.
> HOWEVER - when I try to use the matcher in clang-tidy it will not work. It
> is because of the callee(memberExpr(has(declRefExpr().bind("str1"))))
> part of the matcher. If I remove that, I can match on the
> str1.compare(str2) from the code. But I need to bind str1 as well to test
> if it is a string.
>
> Do you  have any idea why a matcher would work in clang-query, but not in
> clang-tidy? It's the same piece of code it is working on. Is there
> something wrong with my matcher (undefined behavior or something)?
>
> Code:
> #include <iostream>
> #include <string>
>
> int main() {
>     std::string str1{"aa"};
>     std::string str2{"bb"};
>
>     if(str1.compare(str2)) {
>         std::cout << "Strings not equal" << std::endl;
>     }
>
>     return 0;
>
> }
>
>
>
>
> On Sun, Nov 27, 2016 at 10:39 PM Piotr Padlewski <
> piotr.padlewski at gmail.com> wrote:
>
> Sorry for writing 3 emails,
> I looked into http://clang.llvm.org/docs/LibASTMatchersReference.html?
> and it seems that matcher
> on :
> Matcher<CXXMemberCallExpr
> <http://clang.llvm.org/doxygen/classclang_1_1CXXMemberCallExpr.html>> ->
> Matcher<Expr <http://clang.llvm.org/doxygen/classclang_1_1Expr.html>>
> InnerMatcher
> would be my candidate to check. If it won't gonna work then send the test
> and AST dump and I will try to help.
>
> Piotr
>
> 2016-11-27 22:35 GMT+01:00 Piotr Padlewski <piotr.padlewski at gmail.com>:
>
> Adding cfe-dev, because it is related to clang, not LLVM.
>
> 2016-11-27 22:34 GMT+01:00 Piotr Padlewski <piotr.padlewski at gmail.com>:
>
> Hi Mads,
> Can you provide the code that you run clang-query on, or at least AST for
> the fragment you want to match?
>
> Piotr
>
> 2016-11-26 22:27 GMT+01:00 Mads Ravn via llvm-dev <llvm-dev at lists.llvm.org
> >:
>
> Hi,
>
> Hope this is the right channel for this question. I am trying to make an
> ast matcher for clang-tidy to find str1.compare(str2), where both str1 and
> str2 are std::string. I have this so far: http://i.imgur.com/sUma9WC.png .
> But I am having a hard time finding a way to bind an id to the str1 part of
> the expression.
>
> Can anyone help me out with an idea?
>
> Best regards,
> Mads Ravn
>
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