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Stringbufs immutable by default

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* libguile/snarf.h (SCM_IMMUTABLE_STRINGBUF): Remove shared flag.
  Stringbufs are immutable by default.
* libguile/strings.c: Rewrite blurb.  Change to have stringbufs be
  immutable by default and mutable only when marked as such.  Going
  mutable means making a private copy.
  (STRINGBUF_MUTABLE, STRINGBUF_F_MUTABLE): New definitions.
  (SET_STRINGBUF_SHARED): Remove.
  (scm_i_print_stringbuf): Simplify to just alias the stringbuf as-is.
  (substring_with_immutable_stringbuf): New helper.
  (scm_i_substring, scm_i_substring_read_only, scm_i_substring_copy):
  use new helper.
  (scm_i_string_ensure_mutable_x): New helper.
  (scm_i_substring_shared): Use scm_i_string_ensure_mutable_x.
  (stringbuf_write_mutex): Remove; yaaaaaaaay.
  (scm_i_string_start_writing): Use scm_i_string_ensure_mutable_x.  No
  more mutex.
  (scm_i_string_stop_writing): Now a no-op.
  (scm_i_make_symbol): Use substring/copy.
  (scm_sys_string_dump, scm_sys_symbol_dump): Update.
* libguile/strings.h (SCM_I_STRINGBUF_F_SHARED): Remove.
  (SCM_I_STRINGBUF_F_MUTABLE): Add.
* module/system/vm/assembler.scm (link-data): Don't add shared flag any
  more.  Existing compiled flags are harmless tho.
* test-suite/tests/strings.test ("string internals"): Update.
This commit is contained in:
Andy Wingo 2017-02-16 12:57:46 +01:00
commit d0934df1f2
5 changed files with 158 additions and 214 deletions
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34
test-suite/tests/strings.test
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@ -111,27 +111,45 @@
(not (eq? (assq-ref (%string-dump s2) 'shared)
s1))))
(pass-if "ASCII substrings share stringbufs before copy-on-write"
(pass-if "ASCII substrings immutable before copy-on-write"
(let* ((s1 "foobar")
(s2 (substring s1 0 3)))
(assq-ref (%string-dump s1) 'stringbuf-shared)))
(and (not (assq-ref (%string-dump s1) 'stringbuf-mutable))
(not (assq-ref (%string-dump s2) 'stringbuf-mutable)))))
(pass-if "BMP substrings share stringbufs before copy-on-write"
(pass-if "BMP substrings immutable before copy-on-write"
(let* ((s1 "\u0100\u0101\u0102\u0103\u0104\u0105")
(s2 (substring s1 0 3)))
(assq-ref (%string-dump s1) 'stringbuf-shared)))
(and (not (assq-ref (%string-dump s1) 'stringbuf-mutable))
(not (assq-ref (%string-dump s2) 'stringbuf-mutable)))))
(pass-if "ASCII substrings don't share stringbufs after copy-on-write"
(pass-if "ASCII base string still immutable after copy-on-write"
(let* ((s1 "foobar")
(s2 (substring s1 0 3)))
(string-set! s2 0 #\F)
(not (assq-ref (%string-dump s2) 'stringbuf-shared))))
(and (not (assq-ref (%string-dump s1) 'stringbuf-mutable))
(assq-ref (%string-dump s2) 'stringbuf-mutable))))
(pass-if "BMP substrings don't share stringbufs after copy-on-write"
(pass-if "BMP base string still immutable after copy-on-write"
(let* ((s1 "\u0100\u0101\u0102\u0103\u0104\u0105")
(s2 (substring s1 0 3)))
(string-set! s2 0 #\F)
(not (assq-ref (%string-dump s2) 'stringbuf-shared))))
(and (not (assq-ref (%string-dump s1) 'stringbuf-mutable))
(assq-ref (%string-dump s2) 'stringbuf-mutable))))
(pass-if "ASCII substrings mutable after shared mutation"
(let* ((s1 "foobar")
(s2 (substring/shared s1 0 3)))
(string-set! s2 0 #\F)
(and (assq-ref (%string-dump s1) 'stringbuf-mutable)
(assq-ref (%string-dump s2) 'stringbuf-mutable))))
(pass-if "BMP substrings mutable after shared mutation"
(let* ((s1 "\u0100\u0101\u0102\u0103\u0104\u0105")
(s2 (substring/shared s1 0 3)))
(string-set! s2 0 #\F)
(and (assq-ref (%string-dump s1) 'stringbuf-mutable)
(assq-ref (%string-dump s2) 'stringbuf-mutable))))
(with-test-prefix "encodings"