Numbers are stable and cited from source comments; #16 is folded into #12 and keeps its number.

#	Banned
1	`strlen`
2	`<stdlib.h>` `<cstdlib>` `malloc` `calloc` `realloc` `free` `aligned_alloc` `atoi` `atol` `atoll` `strtol` `strtoll` `strtoul` `strtoull` `strtod` `strtof` `qsort` `rand` `srand`
3	`auto`
4	`delay`
5	`millis`
6	`udp_` `tcp_` `pbuf` outside `transport/` and `tls/`, and any outside networking library
7	U+2014
8	`gmtime` `localtime` `ctime` `asctime`
9	`(int)` `(byte)` `(uint8_t)` on an enum member
10	signed `+` `*` `<<` that can overflow
11	a declaration with no initializer, except `extern const <Name>Ns` for a `typedef struct` namespace
12	a file-scope mutable outside one `<Name>Ctx`
13	an alias, a wrapper, a second spelling
14	British spelling
15	a repeated string literal
16	(see #12)
17	`#include` after code
18	`constexpr`
19	`T name[N]` at function scope
20	`snprintf` `vsnprintf`
21	an unbraced `if` `else` `for` `while` body
22	`virtual` `: public` `: protected` `: private` `dynamic_cast` `typeid` `std::function`
23	`?:`
24	`memcpy` `memmove` `memcmp` `memchr` `memset`
25	`<stdio.h>` `<cstdio>` `<string.h>` `<cstring>`