How Structs Really Work in C
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How Structs Really Work in C
1–10 of 14 posts
Re: How Structs Really Work in C
#2Wouldn't the zero-length array potentially run into other memory?
Re: How Structs Really Work in C
#3Wouldn't the zero-length array potentially run into other memory?
It is only fit to be used for heap allocation, you allocate the size that you need (i.e. malloc( sizeof(struct video_file2) + ARRAY_SIZE) ). It wouldn't work as a local variable.
edit: I suppose one could use for globals or on the stack by casting a byte array ... I would find that to be unspeakably ugly but I don't write much C.
Re: How Structs Really Work in C
#4Wouldn't the zero-length array potentially run into other memory?
zero-length arrays, FYI, are not a C thing, they are a GCC thing: http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
C99 has its own "zero sized array" thing but it is a different syntax.
Re: How Structs Really Work in C
#5Wouldn't the zero-length array potentially run into other memory?
That's why the usage changes to a struct pointer at that point. The struct pointer just maps parts of an existing data structure (like a video file) to its labels.
Re: How Structs Really Work in C
#6Most seasoned C programmers understand every point in this post. Points 2 and 3 are indeed clever tricks, but they're tricks that you eventually have to employ if you're doing low level work. It's part of the beauty and allure of C.
Re: How Structs Really Work in C
#7Padding is not allowed at the start of a struct, and some architectures simply can't access misaligned objects.
Re: How Structs Really Work in C
#8Meta comment:
"You don't know it yet, but you're...wrong."
I really really hate it when a posting starts off like this, then proceeds to tell me something anyone who considered themselves a C programmer would know.
Want to write a post about something kind of neat that people outside the field might not be up on? Cool, have fun. But don't start it out by being a rude ass. And this guy dedicates the first hundred words or so of his article to it.
Re: How Structs Really Work in C
#9Packing a struct can reduce performance due to misaligned reads. If the compiler decides your struct needs padding it probably does.
Re: How Structs Really Work in C
#10Any decent C programmer should know this stuff.
Also,
> size_t offset = (size_t) &(((struct s*)0)->thing);
In what universe is that code "ugly"?