How do you initialize a struct with struct members?

Question

In C, is there any way to initialize a struct member struct with a variable, or must I initialize with another initialize list? I realize the wording of these questions is terribly confusing, so here's a trivialized code example

#define MAX_VECTOR_SIZE 10 struct ImmutableVectorC { const short vectorSize; int vectorElements[MAX_VECTOR_SIZE]; }; struct ImportantVectors { struct ImmutableVectorC vec1; struct ImmutableVectorC vec2; struct ImmutableVectorC vec3; struct ImmutableVectorC vec4; struct ImmutableVectorC vec5; }

Suppose I have these structs defined. I want to initialize an ImportantVectors struct with another struct. Is it possible to do something along these lines?

int main() { struct ImmutableVectorC tempStruct = { .vectorSize = (short)2, .vectorElements = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } }; struct ImportantVectors initial = { .vec1 = tempStruct, .vec2 = tempStruct, .vec3 = tempStruct, .vec4 = tempStruct, .vec5 = tempStruct }; }

Visual studio is giving cryptic errors and I'm not sure it it's because these aren't compile-time constants, or some memory management issues, etc.

edit: The error VS gives me is:

error C2440: 'initializing' : cannot convert from 'struct ImmutableVectorC' to 'const short'

And I tried making tempStruct const, but it gives me the same error with the const qualifier in the error message. It does seem to work for primitive members of a struct though (in VS). — xaviersjs
– xaviersjs, Commented Nov 7, 2014 at 15:51
Looks similar to this question: stackoverflow.com/questions/24090739/… in which it is described as a known bug in the compiler — user2404501
– user2404501, Commented Nov 7, 2014 at 15:52

Serge Ballesta · Accepted Answer · 2014-11-07 16:20:29Z

First my MSVC compiler does not really like your code. I have to end all struct element declaration with ; and not , :

struct ImmutableVectorC { short vectorSize; int vectorElements[MAX_VECTOR_SIZE]; }; struct ImportantVectors { struct ImmutableVectorC vec1; struct ImmutableVectorC vec2; struct ImmutableVectorC vec3; struct ImmutableVectorC vec4; struct ImmutableVectorC vec5; };

Next the initialization of tempStruct does not allow for the .name= construct and wants instead :

struct ImmutableVectorC tempStruct = { (short)2, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } };

But the real problem is that my MSVC C compiler does not allow for struct copy in initialization, and insist on having instead :

struct ImportantVectors initial = { { (short)2, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } }, ... };

But I could test using clang and gcc, and both accept field name and struct copy on initialization (but definitively want ; in struct field declaration):

struct ImportantVectors initial2 = { .vec1 = tempStruct, .vec2 = tempStruct, .vec3 = tempStruct, .vec4 = tempStruct, .vec5 = tempStruct, };

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