royzah opened a new pull request, #20199:
URL: https://github.com/apache/nuttx/pull/20199
## Summary
GCC 15 added `-Wunterminated-string-initialization`. Both ChaCha constants
fill their array exactly, leaving no room for the terminator, so the warning
fires and `crypto/Makefile` turns it into an error:
```
chacha_private.h:61:31: error: initializer-string for array of 'char'
truncates
NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16
available) [-Werror=unterminated-string-initialization]
61 | static const char sigma[16] = "expand 32-byte k";
```
Any build of https://github.com/apache/nuttx/blob/master/crypto/chachapoly.c
with that compiler stops there.
## Change
Neither constant is used as a string. Both are read as sixteen bytes through
`U8TO32_LITTLE()`, and `hchacha20()` and `chacha_keysetup()` never look past
index 15. Letting the array size follow the literal keeps them readable, costs
one byte each, and needs no attribute that only some compilers have.
`__attribute__((nonstring))` would be the narrower fix, but
https://github.com/apache/nuttx/blob/master/include/nuttx/compiler.h has no
macro for it and adding one across every compiler block is a larger change than
this warrants. Happy to go that way instead if preferred.
## Testing
Before and after, same file, GCC 15.3.0 for `aarch64-none-elf`:
```
before: 2 diagnostics
after: 0 diagnostics
```
`chacha_keysetup()` then `chacha_ivsetup()` produce a byte-identical
`input[16]` at both 256 and 128 bits:
```
617078653320646e79622d326b20657403020100... (256-bit, before and after)
617078653120646e79622d366b20657403020100... (128-bit, before and after)
```
`tools/nxstyle` clean.
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