Hi, Ph. Marek wrote:
Hello everybody,
I have some structures in my program, where I could save some space by
overlapping them.
See this example:
char *yes_no_auto[]= { "auto", "yes", "no" };
char *yes_no[]= { "yes", "no" };
I know that gcc should fold identical strings in the binary; but if it's
not just strings, but entire structs, this won't help.
Now I wanted to use
char *yes_no_auto[]= { "auto", "yes", "no" };
char *yes_no[]=yes_no_auto+1;
but that doesn't work:
test.c:2: error: invalid initializer
I think this is a more basic issue rather than a gcc issue:Initialization of non scalar values means to allocate a fixed size block of memory on the stack and fill it with values. This is done via the {}- operator .
Your first version fit into this paradigma, but the second one don't.
You have to write:
char *yes_no_auto[]= { "auto", "yes", "no" };
char *yes_no[]= {yes_no_auto[1], yes_no_auto[2]};
to point the entries of your non scalar fixed size array "yes_no" to the
already defined entries in the array "yes_no_auto".
To fill a fixed size scalar value on the stack you have to write:
char *yes_no_auto[]= { "auto", "yes", "no" };
char **yes_no = yes_no_auto + 1;
but then the sizeof operator will only return the size of the scalar
value itself.
Regards, Steve
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