How can we initialize a structure with an array (using its variable)?
This version works well:
MyStruct test = {"hello", 2009};
But this version is bugged:
char str[] = "hello";
MyStruct test = {str, 2009};
views:
89answers:
2
+3
A:
You cannot assign arrays in C, so unfortunately there's no way to do that directly. You may use strcpy to copy the data, though.
typedef struct {
char name[20];
int year;
} MyStruct;
int main() {
MyStruct a = { "hello", 2009 }; // works
char s[] = "hello";
MyStruct b = { "", 2009 }; // use dummy value
strcpy(b.name, s);
return 0;
}
Roger Pate
2009-11-19 22:51:54
I would use strlcpy() or strncpy_s() if available. strncpy() as a semi-last resort. strcpy() only if you know that it won't overflow and feel like making god cry.
asveikau
2009-11-19 22:55:29
Good point. I recommended strcpy because it's standard, he's likely seen it already, and he's guaranteed to have it.
Roger Pate
2009-11-19 22:58:11
Thank you, Roger Pate!
Doug
2009-11-19 22:59:57
You can do array assignments as part of a structure assignment: `struct a { int b[10]; } a, b = { 0 }; a = b;`
Jonathan Leffler
2009-11-19 23:09:00
@asveikau, better use snprintf() instead of strncpy(), this will ensure that your string is nul-terminated.
quinmars
2009-11-20 00:34:13
+1
A:
The definition of MyStruct should contain a first member of type char const *.
Matt Joiner
2009-11-19 22:53:39
Or, slightly more expansively, if the definition of MyStruct contained a char pointer (or, better, a 'const char *'), then the second initializer would work correctly.
Jonathan Leffler
2009-11-19 23:05:32