as of this commit https://core.tcl-lang.org/tcltls/info/2e607e483a6540c8

clang 16 lld musl-c

115.4 ./generic/tls.c:2907:5: error: call to undeclared function 'BIO_cleanup'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
115.4  2907 |     BIO_cleanup();
115.4       |     ^

adding

#include <openssl/bio.h>

allows compiler to proceed but then I get

BIO_cleanup: symbol not found

at package require tls

This is corrected in commit [9e79f40ed58e16f9].