CODEWITHSUNDEEP
c++parsingvisual-c++grammarparser-generator
JavaMan
JavaMan

Reputation: 5034

How to Interpret decl-specifier in the C++ Grammar

I copied the full c++ grammar into my parser generator but is having problems parsing C++ declaration. How should we interpret a decl-specifier when parsing a pointer type declaration like char* varname?

Using MSDN's c++ grammar as an example http://msdn.microsoft.com/en-us/library/0aah9xbf%28v=vs.71%29.aspx:

A specifier is like that:

decl-specifiers :
    decl-specifiersopt decl-specifier
decl-specifier :
    storage-class-specifier
    type-specifier
    fct-specifier
    friend
    typedef
    __declspec ( extended-decl-modifier-seq )

Acccording to that msdn's description char *lpszAppName; should have a decl-specifier = "char * ", name = "lpszAppName". But my test run shows that the decl-specifier should be char, the declarator (i.e. name) should be " * lpszAppName" . Note that the asterisk precedes the name - NOT FOLLOWING the type keyword char. This test result seems reasonable as under decl-specifier, I cannot find anything defining a pointer i.e. there is no rule under the decl-speciifer that can lead to a ptr-operator.

I tested with ANTLR4 parser generator with the full c++ grammar copied from the specification to parse this:

char * 
testfunction(int *cx)
{
  return;
}

The resultant parse tree is like this:

parse tree

Clearly a return type "char *" is actually parsed as return type "char" i.e. a node under the decl-specifier, while the * is associated with the function name i.e. a node under the declarator. The (int* cx ) parameter declaration is also considered type "int" while the pointer * is a node under the declarator for cx.

Is my test correct? If yes, then what should be the grammar looks like if we have to support Visual C++ specific function modifier keywords like __cdecl, __stdcall, or __fastcall e.g.

char * __fastcall
testfunction(int *cx)
{
  return;
}

Clearly, the syntax requires the "char*" be really treated as a type i.e. a node under abstract-declarator.

Upvotes: 1

Views: 836

Answers (1)

MSalters
MSalters

Reputation: 179877

Consider the famous char* x, y; declaration. y is a char, not a char*. The reason is that the * applies to x only. The decl-specifier indeed is just char.

Upvotes: 0

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