Re: JSON/YAML/TOML/etc. parsing performance

[Paul Eggert]

On 10/04/2017 12:38 PM, Eli Zaretskii wrote:
> if we did use size_t for the arguments which can clearly only be
> non-negative, the problems which we are discussing would not have
> happened
Sure, but we would also have worse problems, as size_t is inherently 
more error-prone. ptrdiff_t overflows are reliably diagnosed when Emacs 
is compiled with suitable GCC compiler options. size_t overflows cannot 
be diagnosed, are all too common, and can cause serious trouble.

The Emacs internals occasionally use size_t because underlying 
primitives like 'malloc' do, so we do make some exceptions. Perhaps 
there should be an exception here, for convenience with the JSON 
library. The code snippets I've seen so far in this thread are not 
enough context to judge whether an exception would be helpful in this 
case. Generally speaking, though, unsigned types should be avoided 
because they are more error-prone. This has long been the style in Emacs 
internals, and it's served us well.

(Ironically, just last week I was telling beginning students to beware 
unsigned types, with (0u < -1) as an example....)