c++ - What does 'char x[]' mean? -

i have struct this:

struct  {      char x[]; }; 

what mean? when like:

a a; a.x = "hello"; 

gcc throws error saying:

error: incompatible types in assignent of 'const char [6]' 'char [0u]' 

this c99 "flexible array member". see here gcc specifics: http://www.delorie.com/gnu/docs/gcc/gcc_42.html