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Fix GC bug causing incorrect 'format' output (Bug#75754)

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This fixes the correctness bug discovered in bug#75754, but not the
performance issue or excessive stack usage.

* src/editfns.c (styled_format): Split 'info' array into two arrays,
one of them allocated via SAFE_ALLOCA_LISP for GC protection.
This commit is contained in:
Pip Cet 2025-01-22 19:08:02 +00:00
parent 990b0811ad
commit ed5067e689
1 changed files with 13 additions and 12 deletions
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25
src/editfns.c
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@ -3431,10 +3431,6 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
/* Information recorded for each format spec. */
struct info
{
/* The corresponding argument, converted to string if conversion
was needed. */
Lisp_Object argument;
/* The start and end bytepos in the output string. */
ptrdiff_t start, end;
@ -3461,6 +3457,10 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
|| SIZE_MAX < alloca_size)
memory_full (SIZE_MAX);
info = SAFE_ALLOCA (alloca_size);
/* One argument belonging to each spec; but needs to be allocated
separately so GC doesn't free the strings (bug#75754). */
Lisp_Object *spec_arguments;
SAFE_ALLOCA_LISP (spec_arguments, nspec_bound);
/* discarded[I] is 1 if byte I of the format
string was not copied into the output.
It is 2 if byte I was not the first byte of its character. */
@ -3610,14 +3610,15 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
if (! (n < nargs))
error ("Not enough arguments for format string");
struct info *spec = &info[ispec++];
ptrdiff_t spec_index = ispec++;
struct info *spec = &info[spec_index];
if (nspec < ispec)
{
spec->argument = args[n];
spec_arguments[spec_index] = args[n];
spec->intervals = false;
nspec = ispec;
}
Lisp_Object arg = spec->argument;
Lisp_Object arg = spec_arguments[spec_index];
/* For 'S', prin1 the argument, and then treat like 's'.
For 's', princ any argument that is not a string or
@ -3630,7 +3631,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
if (EQ (arg, args[n]))
{
Lisp_Object noescape = conversion == 'S' ? Qnil : Qt;
spec->argument = arg = Fprin1_to_string (arg, noescape, Qnil);
spec_arguments[spec_index] = arg = Fprin1_to_string (arg, noescape, Qnil);
if (STRING_MULTIBYTE (arg) && ! multibyte)
{
multibyte = true;
@ -3648,7 +3649,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
multibyte = true;
goto retry;
}
spec->argument = arg = Fchar_to_string (arg);
spec_arguments[spec_index] = arg = Fchar_to_string (arg);
}
if (!EQ (arg, args[n]))
@ -3658,7 +3659,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
if (SYMBOLP (arg))
{
spec->argument = arg = SYMBOL_NAME (arg);
spec_arguments[spec_index] = arg = SYMBOL_NAME (arg);
if (STRING_MULTIBYTE (arg) && ! multibyte)
{
multibyte = true;
@ -4303,9 +4304,9 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
for (ptrdiff_t i = 0; i < nspec; i++)
if (info[i].intervals)
{
len = make_fixnum (SCHARS (info[i].argument));
len = make_fixnum (SCHARS (spec_arguments[i]));
Lisp_Object new_len = make_fixnum (info[i].end - info[i].start);
props = text_property_list (info[i].argument,
props = text_property_list (spec_arguments[i],
make_fixnum (0), len, Qnil);
props = extend_property_ranges (props, len, new_len);
/* If successive arguments have properties, be sure that