Write MRB_STR_BINARY through accessors, as the other flags are - #7150

include/mruby/string.h gives each string flag a named way in and out. Three of the four are complete, and one is not:

Because the two are missing, every place that turns the binary flag on or off reaches past the header and names the bit itself. Before this change:

$ grep -rn "flags |= MRB_STR_BINARY\|flags &= ~MRB_STR_BINARY" . --include='*.c'
mrbgems/mruby-encoding/src/encoding.c:72:    s->flags |= MRB_STR_BINARY;
mrbgems/mruby-encoding/src/encoding.c:75:    s->flags &= ~MRB_STR_BINARY;
mrbgems/mruby-regexp/src/regexp.c:1166:  mrb_str_ptr(result)->flags |= MRB_STR_BINARY;
mrbgems/mruby-sprintf/src/sprintf.c:362:  if (p < e) r->flags |= MRB_STR_BINARY;
mrbgems/mruby-string-ext/src/string.c:32:    mrb_str_ptr(str)->flags |= MRB_STR_BINARY;
mrbgems/mruby-string-ext/src/string.c:128:  if (p < e) r->flags |= MRB_STR_BINARY;
mrbgems/mruby-string-ext/src/string.c:1525:  mrb_str_ptr(str)->flags |= MRB_STR_BINARY;
mrbgems/mruby-string-ext/src/string.c:1917:    mrb_str_ptr(result)->flags |= MRB_STR_BINARY;
mrbgems/mruby-string-ext/src/string.c:1991:    mrb_str_ptr(result)->flags |= MRB_STR_BINARY;
mrbgems/mruby-string-bitops/src/string_bitops.c:430:  mrb_str_ptr(result)->flags |= MRB_STR_BINARY;
src/string.c:1422:    t->flags |= MRB_STR_BINARY;
src/string.c:1854:      str->flags |= MRB_STR_BINARY;
src/string.c:3641:    mrb_str_ptr(ret)->flags |= MRB_STR_BINARY;
src/string.c:3882:    mrb_str_ptr(result)->flags |= MRB_STR_BINARY;

Fourteen sites, one src file and five gems. After it, the same grep finds the two macro bodies in the header and nothing else.

What this adds

#define RSTR_SET_BINARY_FLAG(s) ((s)->flags |= MRB_STR_BINARY)
#define RSTR_UNSET_BINARY_FLAG(s) ((s)->flags &= ~MRB_STR_BINARY)

They sit next to RSTR_BINARY_P() rather than inside the #ifdef MRB_UTF8_STRING block the other three flags' accessors are in. A build without MRB_UTF8_STRING still tells a byte read string from the rest, and String#b and String#force_encoding("BINARY") still write the flag there, so the accessors have to be real in that build, exactly as RSTR_BINARY_P() already is.

RSTR_COPY_BINARY_FLAG() keeps the body it has. Expressing it through the new unset would change what it compiles to and buy nothing: this change adds the two ways in that were missing, it does not rebuild the ones already there.

What this changes

• Generated code: nothing. Each macro expands to the expression its call sites spelled out, so only parentheses move. gcc -S -O3 with the full-core defines over the six sources that change gives assembly identical to the assembly before this change, byte for byte.
• Public header: two lines. lib/mruby/amalgam.rb inlines include/mruby/string.h whole, so the amalgamated header gains them too. Nothing is removed or renamed, so code outside this repository is unaffected.
• Ruby level behavior: none. No new test comes with this change, because there is no new answer to pin.

Testing

• full-core gembox, MRB_UTF8_STRING on: 2286 tests, 2276 OK, 10 skip, 0 KO, 0 crash, no new warnings.
• default gembox, where mruby-encoding is absent and strings index by byte: 2070 tests, 2042 OK, 28 skip, 0 KO, 0 crash.

Still left out

Two writes to other string flags still name the bit directly. Neither is a binary flag write, and each wants its own reasoning:

• mrbgems/mruby-string-ext/src/string.c, in str_ascii_only_p(): flags |= MRB_STR_SINGLE_BYTE, where RSTR_SET_SINGLE_BYTE_FLAG() exists but compiles to nothing without MRB_UTF8_STRING, so swapping it in is a behavior question, not a spelling one.
• mrbgems/mruby-sprintf/src/sprintf.c, around line 624: RSTR_SET_EMBED_LEN() written out by hand, next to a branch that sets the heap length to a different value. Folding the pair into RSTR_SET_LEN() is not a rename.

Summary by CodeRabbit

• Bug Fixes
  • Improved consistency when handling binary strings across string, encoding, regular expression, formatting, and bit-operation features.
  • Preserved binary-string behavior during concatenation, replacement, appending, substitution, conversion, and byte manipulation.
• Refactor
  • Standardized internal handling of binary-string status for more reliable behavior across supported operations.