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I've seen a lot of questions on this but I'm going to ask the question differently without specific code. Is there a way of EASILY determining what is causing the type to be incomplete? In my case I'm using someone elses code and I'm completely sure I don't have the headers right, but (since computers do this stuff much faster and better than human eyeballs) is there a way to get the compiler to say, "hey you think you have type X at line 34 but that's actually missing." The error itself only shows up when you assign, which isn't very helpful.
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The “dereferencing pointer to incomplete type” error commonly occurs in C when one tries to dereference a type (usually a struct) that is: not declared at all. declared, but not defined.
Dereferencing is used to access or manipulate data contained in memory location pointed to by a pointer. *(asterisk) is used with pointer variable when dereferencing the pointer variable, it refers to variable being pointed, so this is called dereferencing of pointers.
In C++, we must explicitly typecast return value of malloc to (int *). 2) void pointers in C are used to implement generic functions in C. For example compare function which is used in qsort(). Some Interesting Facts: 1) void pointers cannot be dereferenced.
Dereferencing is getting at the pointed value. Pointer variables are useful for walking the contents of a linked list data structure, using a dynamic jump table to subroutines, and passing arguments by address (so only an address is passed) rather than by value (where the entire data structure is copied).
I saw a question the other day where someone inadvertently used an incomplete type by specifying something like
struct a { int q; }; struct A *x; x->q = 3; The compiler knew that struct A was a struct, despite A being totally undefined, by virtue of the struct keyword.
That was in C++, where such usage of struct is atypical (and, it turns out, can lead to foot-shooting). In C if you do
typedef struct a { ... } a; then you can use a as the typename and omit the struct later. This will lead the compiler to give you an undefined identifier error later, rather than incomplete type, if you mistype the name or forget a header.
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Another possible reason is indirect reference. If a code references to a struct that not included in current c file, the compiler will complain.
a->b->c //error if b not included in current c file
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