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C++: Variables and prototypes #742

Merged
merged 3 commits into from
Jan 4, 2016
Merged

C++: Variables and prototypes #742

merged 3 commits into from
Jan 4, 2016

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pragmaware
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Local function prototypes are unlikely and the current code generates many false tags (things that aren't actually prototypes). Silence them. Try to catch variable instantiations in the form 'Type var(params)' instead, which are far more common.

@pragmaware
C++: Local function prototypes are unlikely and the current code gene…
0c5ba53 
…rates many false tags (things that aren't actually prototypes). Silence them. Try to catch variable instantiations in the form 'Type var(params)' instead, which are far more common.
@pragmaware
Add a test for the prototype silencing
2c23f32
@masatake
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Could you rename variables-prototypes-2.cpp.b directory to variables-prototypes-2.cpp.d?
.b is for recording known bugs. Your commit fixes the bug.

https://travis-ci.org/universal-ctags/ctags/jobs/98898723

FIXED:                                 1

    parser-cpp.r/variables-prototypes-2.cpp

@pragmaware
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Done.

@masatake
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After introducing your commit, the result of Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp is
changed. I have to think about this more.

% diff -ruN <(./3d596a4-ctags --c++-kinds=+pl --fields=+S -o - Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp ) <(./deea228-ctags --c++-kinds=+pl --fields=+S -o - Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp )
<s=+S -o - Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp )
--- /proc/self/fd/11    2015-12-31 09:49:22.339998919 +0900
+++ /proc/self/fd/12    2015-12-31 09:49:22.340998890 +0900
@@ -30,33 +30,8 @@
 X9 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^int X9( a && b );                       \/\/variable$/;"  p   file:   signature:( a && b )
 a1 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int  a1 = i < 7 ? i : 7;$/;"  l
 a5 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int  a5 = 8;$/;"  l
-a7 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int  a7( short ( *p )( int ) );$/;"   p   file:   signature:( short ( *p )( int ) )
 a8 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    short a8 = i;$/;" l
-b2 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int b2( int ooo, const char* o );       \/\/prototype$/;" p   file:   signature:( int ooo, const char* o )
-b3 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int b3( int( 7 ) );                     \/\/variable$/;"  p   file:   signature:( int( 7 ) )
-c2 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int c2( int * h );                      \/\/prototype$/;" p   file:   signature:( int * h )
-c4 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int c4( std::map<int> a );              \/\/prototype$/;" p   file:   signature:( std::map<int> a )
-c5 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int c5( map<int>  & a );                \/\/prototype$/;" p   file:   signature:( map<int> & a )
-c6 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int c6( ooo & a );                      \/\/prototype$/;" p   file:   signature:( ooo & a )
-c7 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int c7( int & a );                      \/\/prototype$/;" p   file:   signature:( int & a )
-c8 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int c8( map<int> a );                   \/\/prototype$/;" p   file:   signature:( map<int> a )
-c9 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int c9( int a );                        \/\/prototype$/;" p   file:   signature:( int a )
-f1 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int f1( SomeType (*p)( int ) );         \/\/prototype$/;" p   file:   signature:( SomeType (p) int ) )
-f3 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int f3( std::map<int> & a );            \/\/prototype$/;" p   file:   signature:( std::map<int> & a )
-g1 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int g1( SomeType a );                   \/\/prototype$/;" p   file:   signature:( SomeType a )
-h1 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    char h1( const char *a = "a" );         \/\/prototype$/;" p   file:   signature:( const char *a = R )
-h2 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int h2();                               \/\/prototype$/;" p   file:   signature:()
-h3 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    char h3( double );                      \/\/prototype$/;" p   file:   signature:( double )
-h4 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int h4( h u );                          \/\/prototype$/;" p   file:   signature:( h u )
-iii    Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int v5( iii( o ) );                     \/\/variable$/;"  p   file:   signature:(o )
 iii    Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^int V5( iii( o ) );                     \/\/variable$/;"  p   file:   signature:(o )
 j  Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^int D3( *j );                           \/\/variable$/;"  v
 main   Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^int  main( int  argc, char ** argv )$/;"  f   signature:( int argc, char ** argv )
-v6 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int v6( int (*p)( int ) );              \/\/prototype$/;" p   file:   signature:( int (*p)( int ) )
-v8 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int v8( ooo );                          \/\/variable$/;"  p   file:   signature:( ooo )
-w1 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int w1 __ARGS (( int a ));              \/\/prototype$/;" p   file:   signature:( int a )
-w2 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int w2 (( a - 5 ) \/ 6 );                \/\/variable$/;" p   file:   signature:( a - 5 ) / 6 
-x1 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int x1( a.b );                          \/\/variable$/;"  p   file:   signature:( a.b )
-x3 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int x3( NS::a  b );                     \/\/prototype$/;" p   file:   signature:( NS::a b )
-x4 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int x4( a ^ b );                        \/\/variable $/;" p   file:   signature:( a ^ b )
-x9 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int x9( a && b );                       \/\/variable$/;"  p   file:   signature:( a && b )
+w1 Units/parser-cpp.r/variables-prototypes.cpp.b/input.cpp /^    int w1 __ARGS (( int a ));              \/\/prototype$/;" l

@pragmaware
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Yes, it has.
All the "nested" function prototypes are gone but we have gained the local variable declarations in the form of Type name(parameters). The rationale is:

  • The current cpp parser is too hard to fix in order to handle both forms. It would require a lot of tweaking and with multiple languages in place it's simply not feasible.
  • Nested function prototypes are very uncommon (almost no program has them)
  • The current parser finds many false nested function prototypes. Almost everything
    in the form Anything(something) is seen as prototype. This is wrong.
  • Local variable declarations in the form of instantiation are extremely common

So the net result is:

  • Removed many false tags
  • Lost some correct but very uncommon tags
  • Gained many correct common tags

In sum: a gain.

masatake added a commit that referenced this pull request Jan 4, 2016
@masatake
Merge pull request #742 from pragmaware/variables-and-prototypes
ac891bf 
C++: Variables and prototypes
@masatake masatake merged commit ac891bf into universal-ctags:master Jan 4, 2016
@masatake
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masatake commented Jan 4, 2016

Fair enough. Thank you.

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@pragmaware @masatake