Why enclose blocks of C code in curly braces?
Legacy code needed { } in order to do declarations at all
In C89, you couldn't just do int i; anywhere; declarations were only valid at the beginning of blocks.
So:
a = 1;int i; /* error */i = 2;...wasn't valid, but
a = 1if (e) { int i;...was fine, as was a plain block.
The resulting style continued even after declarations became valid (C99) block-item(s), partly by inertia, partly for backwards portability, and also because it makes sense to establish a scope for new declarations.
To scope variables. E.g. the variable tmp_argv will only be valid between the braces.
Another use case for this I've recently discovered is when you have open/close semantics and you want to clearly mark the 'inner' code:
f = fopen('file');{ // do stuff}fclose(f);This works well to remind you to close/free objects and a makes the code somewhat cleaner.