Skip to content

string.c: keep what a string reads as across a write that cannot change it #7180

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
matz merged 1 commit into from
Aug 15, 2026
Merged

string.c: keep what a string reads as across a write that cannot change it #7180

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 32 additions & 8 deletions src/string.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1258,9 +1258,9 @@ mrb_str_modify_keep_ascii(mrb_state *mrb, struct RString *s)
{
mrb_check_frozen(mrb, s);
str_unshare_buffer(mrb, s);
/* Every in-place write reaches here, including the ones that keep the string
ASCII, so this is where the walk's answer stops holding. What a string of
nothing but ASCII stands at is the caller's to keep. */
/* A write that leaves the string holding nothing but ASCII leaves it
standing where it stood, and that is the caller's to keep. Anything else
the bytes were read as stops holding here. */
if (RSTR_CODERANGE(s) != MRB_STR_CODERANGE_7BIT) {
RSTR_CODERANGE_SET(s, MRB_STR_CODERANGE_UNKNOWN);
}
Expand All @@ -1282,6 +1282,30 @@ mrb_str_modify(mrb_state *mrb, struct RString *s)
RSTR_CODERANGE_SET(s, MRB_STR_CODERANGE_UNKNOWN);
}

/* mrb_str_modify() for a caller whose write leaves what the bytes read as
standing: it puts ASCII where ASCII stood, or it cuts where a character
ends. Such a write cannot turn a sound string unsound, so the answer the
string came in carrying is still the answer, and the next asker is spared
the walk that would arrive at it again.

Only a string already read as broken has to be asked again, since a write
is as likely to have mended it as to have left it broken. A string that
the write leaves holding nothing but ASCII keeps saying VALID rather than
moving to 7BIT: that is an answer worth less than the truth, not a wrong
one, and finding the truth is the walk this is here to skip.

The promise this asks of its caller cannot be checked here, which is why
it is not offered outside the library. */
static void
str_modify_keep_cr(mrb_state *mrb, struct RString *s)
{
mrb_check_frozen(mrb, s);
str_unshare_buffer(mrb, s);
if (RSTR_CODERANGE(s) == MRB_STR_CODERANGE_BROKEN) {
RSTR_CODERANGE_SET(s, MRB_STR_CODERANGE_UNKNOWN);
}
}

/*
* @param mrb The mruby state.
* @param str The mruby string to resize.
Expand Down Expand Up @@ -2016,7 +2040,7 @@ mrb_str_capitalize_bang(mrb_state *mrb, mrb_value str)
struct RString *s = mrb_str_ptr(str);
mrb_int len = RSTR_LEN(s);

mrb_str_modify_keep_ascii(mrb, s);
str_modify_keep_cr(mrb, s);
char *p = RSTR_PTR(s);
char *pend = RSTR_PTR(s) + len;
if (len == 0 || p == NULL) return mrb_nil_value();
Expand Down Expand Up @@ -2069,7 +2093,7 @@ mrb_str_chomp_bang(mrb_state *mrb, mrb_value str)
mrb_int argc = mrb_get_args(mrb, "|S", &rs);
struct RString *s = mrb_str_ptr(str);

mrb_str_modify_keep_ascii(mrb, s);
str_modify_keep_cr(mrb, s);
mrb_int len = RSTR_LEN(s);
if (argc == 0) {
if (len == 0) return mrb_nil_value();
Expand Down Expand Up @@ -2177,7 +2201,7 @@ mrb_str_chop_bang(mrb_state *mrb, mrb_value str)
{
struct RString *s = mrb_str_ptr(str);

mrb_str_modify_keep_ascii(mrb, s);
str_modify_keep_cr(mrb, s);
if (RSTR_LEN(s) > 0) {
mrb_int len;
#ifdef MRB_UTF8_STRING
Expand Down Expand Up @@ -2249,7 +2273,7 @@ mrb_str_downcase_bang(mrb_state *mrb, mrb_value str)
mrb_bool modify = FALSE;
struct RString *s = mrb_str_ptr(str);

mrb_str_modify_keep_ascii(mrb, s);
str_modify_keep_cr(mrb, s);
p = RSTR_PTR(s);
pend = RSTR_PTR(s) + RSTR_LEN(s);
while (p < pend) {
Expand Down Expand Up @@ -3428,7 +3452,7 @@ mrb_str_upcase_bang(mrb_state *mrb, mrb_value str)
char *p, *pend;
mrb_bool modify = FALSE;

mrb_str_modify_keep_ascii(mrb, s);
str_modify_keep_cr(mrb, s);
p = RSTRING_PTR(str);
pend = RSTRING_END(str);
while (p < pend) {
Expand Down
Loading