C++ Struct internal declaration confusion?

Question

I've come across a declaration inside a C++ Struct{..} that I've never seen before. Can anyone tell me what it means;

struct DerivedMesh {

char cd_flag;

void (*calcNormals)(DerivedMesh *dm); // <-- What is this?

It kind of looks like it's dereferencing a pointer called calcNormals, but that's all I can make out.

Looks like a function pointer to me, a pointer to a function that accepts a `DerivedMesh *dm` parameter, and returns void. — Serge, Aug 22 '14 at 16:06
Relevant: [Spiral Rule](http://c-faq.com/decl/spiral.anderson.html) — chris, Aug 22 '14 at 16:07
its function pointer - a pointer to hold the address of a function of certain signature — resultsway, Aug 22 '14 at 18:29

score 2 · Answer 1 · answered Aug 22 '14 at 16:06

This is a C syntax for declaring function pointers.

In this particular example, DerivedMesh will have a member calcNormals that is a pointer to a function accepting single argument of type DerivedMesh*. It can be called like an ordinary function:

void foo(DerivedMesh* dm) { ... }

DerivedMesh dm;;
// Init members and set calcNormals to actual function
dm.cf_flag = whatever;
dm.calcNormals = foo;
dm.calcNormals(&dm); // calls foo

score 0 · Answer 2 · answered Aug 22 '14 at 16:11

0

This

void (*calcNormals)(DerivedMesh *dm);

is class data member definition with name calcNormals that has type of pointer to function of type void( DerivedMesh * )

answered Aug 22 '14 at 16:11

Vlad from Moscow

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C++ Struct internal declaration confusion?

2 Answers2