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replace-region-contents malloc fallback

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* src/editfns.c (Freplace_region_contents): If the temporary
storage is so large that malloc fails, do not signal an error.
Instead, fall back on destructive replacement.
This commit is contained in:
Paul Eggert 2026-06-06 16:43:45 -07:00 committed by Pip Cet
parent 90f25503d8
commit f5cb95423e
2 changed files with 72 additions and 56 deletions
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2
doc/lispref/text.texi
View file

@ -4863,7 +4863,7 @@ faster but suboptimal solution. The default value is 1000000.
@code{replace-region-contents} returns @code{t} if a non-destructive
replacement could be performed. Otherwise, i.e., if @var{max-secs}
was exceeded, it returns @code{nil}.
was exceeded or too much memory would have been needed, it returns @code{nil}.
Note: When using the refined replacement algorithm, if the replacement
is a string, it will be internally copied to a temporary buffer.

126
src/editfns.c
View file

@ -1961,8 +1961,8 @@ in a temporary buffer. Therefore, all else being equal, it is preferable
to pass a buffer rather than a string as SOURCE argument.
This function returns t if a non-destructive replacement could be
performed. Otherwise, i.e., if MAX-SECS was exceeded, it returns
nil.
performed. Otherwise, i.e., if MAX-SECS was exceeded or too much
memory would have been needed, it returns nil.
SOURCE can also be a function that will be called with no arguments
and with current buffer narrowed to BEG..END, and should return
@ -2065,6 +2065,18 @@ a buffer or a string. But this is deprecated. */)
time_limit = tlim;
}
/* The rest of the code is not prepared to handle a string SOURCE. */
if (!b)
{
Lisp_Object workbuf
= code_conversion_save (true, STRING_MULTIBYTE (source));
b = XBUFFER (workbuf);
set_buffer_internal (b);
CALLN (Finsert, source);
set_buffer_internal (a);
}
Lisp_Object source_buffer = make_lisp_ptr (b, Lisp_Vectorlike);
specpdl_ref count = SPECPDL_INDEX ();
ptrdiff_t diags = size_a + size_b + 3;
@ -2078,60 +2090,65 @@ a buffer or a string. But this is deprecated. */)
ptrdiff_t bytes_needed;
if (ckd_mul (&bytes_needed, diags, bytes_per_diag)
|| ckd_add (&bytes_needed, bytes_needed,
align_bytes - surplus_char_bytes + del_bytes + ins_bytes))
memory_full_up ();
USE_SAFE_ALLOCA;
buffer = SAFE_ALLOCA (bytes_needed);
/* The rest of the code is not prepared to handle a string SOURCE. */
if (!b)
align_bytes - surplus_char_bytes + del_bytes + ins_bytes)
|| SIZE_MAX < bytes_needed)
buffer = NULL;
else if (bytes_needed <= MAX_ALLOCA)
buffer = alloca (bytes_needed);
else
{
Lisp_Object workbuf
= code_conversion_save (true, STRING_MULTIBYTE (source));
b = XBUFFER (workbuf);
set_buffer_internal (b);
CALLN (Finsert, source);
set_buffer_internal (a);
buffer = malloc (bytes_needed);
if (buffer)
{
if (profiler_memory_running)
malloc_probe (bytes_needed);
record_unwind_protect_ptr (xfree, buffer);
}
}
Lisp_Object source_buffer = make_lisp_ptr (b, Lisp_Vectorlike);
/* Copy the characters to arrays of C integers. This speeds up
comparison dramatically in multibyte buffers. */
int *chars_a = (int *) (((uintptr_t) (buffer + 2 * diags) + align_bytes)
& ~align_bytes);
for (ptrdiff_t i = 0; i < size_a; i++)
chars_a[i]
= BUF_FETCH_CHAR_AS_MULTIBYTE (a, buf_charpos_to_bytepos (a, min_a + i));
int *chars_b = chars_a + size_a;
for (ptrdiff_t i = 0; i < size_b; i++)
chars_b[i]
= BUF_FETCH_CHAR_AS_MULTIBYTE (b, buf_charpos_to_bytepos (b, min_b + i));
unsigned char *deletions_insertions = memset (chars_b + size_b, 0,
del_bytes + ins_bytes);
/* FIXME: It is not documented how to initialize the contents of the
context structure. This code cargo-cults from the existing
caller in src/analyze.c of GNU Diffutils, which appears to
work. */
struct context ctx = {
.chars_a = chars_a,
.chars_b = chars_b,
.deletions = deletions_insertions,
.insertions = deletions_insertions + del_bytes,
.fdiag = buffer + size_b + 1,
.bdiag = buffer + diags + size_b + 1,
.heuristic = true,
.too_expensive = too_expensive,
.time_limit = time_limit,
};
/* compareseq requires indices to be zero-based. We add BEGV back
later. */
bool early_abort;
if (! sys_setjmp (ctx.jmp))
early_abort = compareseq (0, size_a, 0, size_b, false, &ctx);
struct context ctx;
if (buffer)
{
/* Copy the characters to arrays of C ints. This speeds up
comparison dramatically in multibyte buffers. */
int *chars_a = (int *) (((uintptr_t) (buffer + 2 * diags) + align_bytes)
& ~align_bytes);
for (ptrdiff_t i = 0; i < size_a; i++)
chars_a[i] = (BUF_FETCH_CHAR_AS_MULTIBYTE
(a, buf_charpos_to_bytepos (a, min_a + i)));
int *chars_b = chars_a + size_a;
for (ptrdiff_t i = 0; i < size_b; i++)
chars_b[i] = (BUF_FETCH_CHAR_AS_MULTIBYTE
(b, buf_charpos_to_bytepos (b, min_b + i)));
unsigned char *deletions_insertions = memset (chars_b + size_b, 0,
del_bytes + ins_bytes);
/* FIXME: It is not documented how to initialize the contents of the
context structure. This code cargo-cults from the existing
caller in src/analyze.c of GNU Diffutils, which appears to
work. */
ctx = (struct context) {
.chars_a = chars_a,
.chars_b = chars_b,
.deletions = deletions_insertions,
.insertions = deletions_insertions + del_bytes,
.fdiag = buffer + size_b + 1,
.bdiag = buffer + diags + size_b + 1,
.heuristic = true,
.too_expensive = too_expensive,
.time_limit = time_limit,
};
/* compareseq wants zero-based indices. We add BEGV back later. */
if (! sys_setjmp (ctx.jmp))
early_abort = compareseq (0, size_a, 0, size_b, false, &ctx);
else
early_abort = true;
}
else
early_abort = true;
@ -2141,8 +2158,7 @@ a buffer or a string. But this is deprecated. */)
make_fixnum (BUF_BEGV (b)),
make_fixnum (BUF_ZV (b)));
replace_range (min_a, min_a + size_a, src, true, false, inh);
SAFE_FREE_UNBIND_TO (count, Qnil);
return Qnil;
return unbind_to (count, Qnil);
}
Fundo_boundary ();
@ -2196,7 +2212,7 @@ a buffer or a string. But this is deprecated. */)
--j;
}
SAFE_FREE_UNBIND_TO (count, Qnil);
unbind_to (count, Qnil);
if (modification_hooks_inhibited)
{