Indexing C projects with clang

Indexing means cross referencing, find definition and all usages of any functions. Writing indexing tool is like writing linker, main job is resolving symbols.

Features implemented

• Go to definition
  • macro
  • function

Known bugs

• Weak symbols: two global functions defined, one is weak, the strong version should take precedence and mark the weak one as declaration. eg. skb_copy_bits in kernel/bpf/core.c.

TODO

• Go to definition
  • struct
  • enum
  • field, also link sk_port in sk->sk_prot->init(sk) to __sk_common.skc_prot not macro sk_port
• Inline
  • macro expansion, with formatting
  • struct size
  • enum member
  • field type
• Find all reference
  • function
  • type
  • field
• Refinement
  • canonical file path: ./include/header.h to include/header.h, bin/../lib/header to lib/header
  • header file using symbolic link
• Output
  • directory navigation
  • file overview
  • mirror directory of source code

No plan to support C++, yet

Use other tools to index your C++ projects:

• kythe
• woboq
• dxr

First enemy of indexing C code: Preprocessing

Almost all difficiulities come from preprocessing especially macro.

• #include MACRO, file included depends on definition of MACRO, hard to insert a link.
• Easy to index macro name, difficiult or impossible to index the content of macro.
• A header may provide different symbols if macros defined before #include change.
• A function may be defined in macro expansion, hard to find a location.