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Author	SHA1	Message	Date
Johannes Sixt	8a2e8da367	userdiff: have 'cpp' hunk header pattern catch more C++ anchor points The hunk header pattern 'cpp' is intended for C and C++ source code, but it is actually not particularly useful for the latter, and even misses some use-cases for the former. The parts of the pattern have the following flaws: - The first part matches an identifier followed immediately by a colon and arbitrary text and is intended to reject goto labels and C++ access specifiers (public, private, protected). But this pattern also rejects C++ constructs, which look like this: MyClass::MyClass() MyClass::~MyClass() MyClass::Item MyClass::Find(... - The second part matches an identifier followed by a list of qualified names (i.e. identifiers separated by the C++ scope operator '::') separated by space or '' followed by an opening parenthesis (with space between the tokens). It matches function declarations like struct item get_head(... int Outer::Inner::Func(... Since the pattern requires at least two identifiers, GNU-style function definitions are ignored: void func(... Moreover, since the pattern does not allow punctuation other than '', the following C++ constructs are not recognized: . template definitions: template<class T> int func(T arg) . functions returning references: const string& get_message() . functions returning templated types: vector<int> foo() . operator definitions: Value operator+(Value l, Value r) - The third part of the pattern finally matches compound definitions. But it forgets about unions and namespaces, and also skips single-line definitions struct random_iterator_tag {}; because no semicolon can occur on the line. Change the first pattern to require a colon at the end of the line (except for trailing space and comments), so that it does not reject constructor or destructor definitions. Notice that all interesting anchor points begin with an identifier or keyword. But since there is a large variety of syntactical constructs after the first "word", the simplest is to require only this word and accept everything else. Therefore, this boils down to a line that begins with a letter or underscore (optionally preceded by the C++ scope operator '::' to accept functions returning a type anchored at the global namespace). Replace the second and third part by a single pattern that picks such a line. This has the following desirable consequence: - All constructs mentioned above are recognized. and the following likely desirable consequences: - Definitions of global variables and typedefs are recognized: int num_entries = 0; extern const char help_text; typedef basic_string<wchar_t> wstring; - Commonly used marco-ized boilerplate code is recognized: BEGIN_MESSAGE_MAP(CCanvas,CWnd) Q_DECLARE_METATYPE(MyStruct) PATTERNS("tex",...) (The last one is from this very patch.) but also the following possibly undesirable consequence: - When a label is not on a line by itself (except for a comment) it is no longer rejected, but can appear as a hunk header if it occurs at the beginning of a line: next:; IMO, the benefits of the change outweigh the (possible) regressions by a large margin. Signed-off-by: Johannes Sixt <j6t@kdbg.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>	11 years ago
Johannes Sixt	9cc444f057	t4018: test cases showing that the cpp pattern misses many anchor points Most of the tests show C++ code, but there is also a union definition and a GNU style function definition that are not recognized. Signed-off-by: Johannes Sixt <j6t@kdbg.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>	11 years ago

Author

SHA1

Message

Date

Johannes Sixt

8a2e8da367

userdiff: have 'cpp' hunk header pattern catch more C++ anchor points

The hunk header pattern 'cpp' is intended for C and C++ source code, but
it is actually not particularly useful for the latter, and even misses
some use-cases for the former.

The parts of the pattern have the following flaws:

- The first part matches an identifier followed immediately by a colon
  and arbitrary text and is intended to reject goto labels and C++
  access specifiers (public, private, protected). But this pattern also
  rejects C++ constructs, which look like this:

    MyClass::MyClass()
    MyClass::~MyClass()
    MyClass::Item MyClass::Find(...

- The second part matches an identifier followed by a list of qualified
  names (i.e. identifiers separated by the C++ scope operator '::')
  separated by space or '*' followed by an opening parenthesis (with
  space between the tokens). It matches function declarations like

    struct item* get_head(...
    int Outer::Inner::Func(...

  Since the pattern requires at least two identifiers, GNU-style
  function definitions are ignored:

    void
    func(...

  Moreover, since the pattern does not allow punctuation other than '*',
  the following C++ constructs are not recognized:

  . template definitions:
      template<class T> int func(T arg)

  . functions returning references:
      const string& get_message()

  . functions returning templated types:
      vector<int> foo()

  . operator definitions:
      Value operator+(Value l, Value r)

- The third part of the pattern finally matches compound definitions.
  But it forgets about unions and namespaces, and also skips single-line
  definitions

    struct random_iterator_tag {};

  because no semicolon can occur on the line.

Change the first pattern to require a colon at the end of the line
(except for trailing space and comments), so that it does not reject
constructor or destructor definitions.

Notice that all interesting anchor points begin with an identifier or
keyword. But since there is a large variety of syntactical constructs
after the first "word", the simplest is to require only this word and
accept everything else. Therefore, this boils down to a line that begins
with a letter or underscore (optionally preceded by the C++ scope
operator '::' to accept functions returning a type anchored at the
global namespace). Replace the second and third part by a single pattern
that picks such a line.

This has the following desirable consequence:

- All constructs mentioned above are recognized.

and the following likely desirable consequences:

- Definitions of global variables and typedefs are recognized:

    int num_entries = 0;
    extern const char* help_text;
    typedef basic_string<wchar_t> wstring;

- Commonly used marco-ized boilerplate code is recognized:

    BEGIN_MESSAGE_MAP(CCanvas,CWnd)
    Q_DECLARE_METATYPE(MyStruct)
    PATTERNS("tex",...)

  (The last one is from this very patch.)

but also the following possibly undesirable consequence:

- When a label is not on a line by itself (except for a comment) it is
  no longer rejected, but can appear as a hunk header if it occurs at
  the beginning of a line:

    next:;

IMO, the benefits of the change outweigh the (possible) regressions by a
large margin.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

11 years ago

Johannes Sixt

9cc444f057

t4018: test cases showing that the cpp pattern misses many anchor points

Most of the tests show C++ code, but there is also a union definition and
a GNU style function definition that are not recognized.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

11 years ago

2 Commits (0f64cc407f32f979c8bcfa7d3d9b24d8e023df35)