[llvm-dev] [cfe-dev] Location (in Source Code) of String Literal in MacroExpansion

[via llvm-dev]

Oh, now I see why you were puzzled!

 

`printf()` expects a null-terminated string (“%s”), but you pass an llvm::StringRef instead, which is not null terminated!

Thus, you will end up with undefined behavior, which ends up printing till the end of the file.

 

I hope this is it!

 

Balazs

 

From: benicsbalazs at gmail.com <benicsbalazs at gmail.com> 
Sent: 2021. augusztus 26., csütörtök 12:25
To: 'chiasa.men' <chiasa.men at web.de>
Cc: llvm-dev at lists.llvm.org
Subject: RE: [cfe-dev] Location (in Source Code) of String Literal in MacroExpansion

 

Hi Chiasa,

 

For the example you attached the MacroExpansionContext seems to work as I intended.

It records what range gets replaced by what tokens at the end of the preprocessing, thus we get

`CONCATMACRO("TEST")` -> ` L"TEST"`

 

About `Lexer::getSourceText()` I’m not sure. I haven’t used that. The `at()` function was designed as a helper defining the unit tests. I might misused something when I created this code & tests, let me know!

 

Balazs

 

From: cfe-dev <cfe-dev-bounces at lists.llvm.org <mailto:cfe-dev-bounces at lists.llvm.org> > On Behalf Of chiasa.men via cfe-dev
Sent: 2021. augusztus 26., csütörtök 10:03
To: cfe-dev <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org> >
Cc: llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> 
Subject: [cfe-dev] Location (in Source Code) of String Literal in MacroExpansion

 

https://gist.github.com/T35R6braPwgDJKq/6439fda090e4ee8440d726f8dafa4dbb#file-mectest-cpp

 

Above I modified the MacroExpansionContext unittest.

The relevant code:

//--------------

TEST_F(MacroExpansionContextTest, Custom) {

  // From the GCC website.

  const auto Ctx = getMacroExpansionContextFor(R"code(

#define CONCATMACRO(parm) L##parm

int f(wchar_t *b){}

int main()

{

    int a= f(CONCATMACRO("TEST"));

    int b= f(L"TEST");

    return 0;

}

)code");

    Ctx->dumpExpansionRanges();

    //> :6:14, :6:33

    Ctx->dumpExpandedTexts();

    //> :6:14 -> 'L"TEST"'

    printf("Exp: %s\n",Ctx->getExpandedText(at(6, 14)).getValue());

    //Exp: L"TEST"

    printf("Org: %s\n",Ctx->getOriginalText(at(6, 14)).getValue());

    //Org: CONCATMACRO("TEST"));

    //    int b= f(L"TEST");

    //    return 0;

    //}

    StringRef sourceText = clang::Lexer::getSourceText(CharSourceRange(SourceRange(at(6, 14),at(6, 33)),false),SourceMgr, LangOpts);

    printf("sourceText: %s\n",sourceText);

    // sourceText: CONCATMACRO("TEST"));

    //     int b= f(L"TEST");

    //     return 0;

    // }

}

//--------------

I am interested in getting the range for "TEST" in the SourceText. Since the CONCATMACRO is preprocessed to L"TEST" I thought the MacroExpansionContext would be of help.

It tells about the ExpansionRanges: 6:14, :6:33 which is CONCATMACRO("TEST")

What I would need is: 6:26, 6:32

Obviously I could just calculate a bit like:

range.begin (14) + macronameLen (11) +1 (opening parenthesis) = 26

to

range.end (33) - 1 (closing parenthesis) = 32

 

But would that be reliable and is there no other way?

 

Furthermore: Why do getSourceText/getOriginalText print the whole rest of the source code and not just from (6,14) to (6,33)?

 

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