C

File-scope function definitions and struct, enum and union types, each bounded by its own braces. Storage-class and inline keywords (static, extern, inline, _Noreturn, …) are stripped before matching, so static inline int clamp( is a function named clamp; a pointer return type is stripped with them, so const char *greeting( names greeting and not its type. The brace may sit on the signature line or on its own line below it, and the signature may span several lines — all three are ordinary C style and all three are bounded correctly.

Two things are deliberately not declarations. A prototype has no body, so it mints no population — a header of 40 prototypes is not 40 declarations. A preprocessor line is skipped whole, so #define MAX(a, b) ((a) > (b) ? (a) : (b)) is not read as a function called MAX; macros are text substitution, and measuring one as a declaration would report a length and a complexity nobody wrote.

Function bodies are stepped over once their end is known, so nothing inside one — if (, for (, a call — can be read as a declaration. Unlike Java, type bodies are not descended into either: C types hold fields, not methods, so there is nothing inside them to grade.

Everything it misses, it misses in the safe direction:

• K&R-style definitions (int add(a, b) with the parameter declarations on following lines) are not recognised. Cost: that one function, not the file.
• Declarations produced by macros — a function defined inside a #define, or a body wrapped in BEGIN_/END_ macros — are invisible.
• .h is treated as C. A C++ header using .h gets the C scanner, which reads its free functions and structs and misses its classes and methods. The C++ increment disambiguates this.
• Conditional compilation is not evaluated. Both arms of an #if/#else are read as ordinary source, so a declaration in a disabled arm still counts.

Complexity for C is the same keyword count used everywhere else here, not a control-flow graph. Pair it with an external analyzer — lizard covers C and is in the shipped pool — when the number has to be exact.