[PATCH 2/2] stdio-common: Remove fallback realloc calls from vscfanf
Florian Weimer
fweimer@redhat.com
Mon Aug 17 10:05:47 GMT 2026
These merely delay the inevitable on 32-bit architectures.
Growing a buffer one character at a time is very slow, so this
could lead to even more processing time for very large inputs.
---
stdio-common/vfscanf-internal.c | 316 +++++++++-----------------------
1 file changed, 82 insertions(+), 234 deletions(-)
diff --git a/stdio-common/vfscanf-internal.c b/stdio-common/vfscanf-internal.c
index e2e08c0eab..a15669f056 100644
--- a/stdio-common/vfscanf-internal.c
+++ b/stdio-common/vfscanf-internal.c
@@ -825,21 +825,9 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
newstr = (char *) realloc (*strptr, strsize * 2);
if (newstr == NULL)
{
- /* Can't allocate that much. Last-ditch effort. */
- newstr = (char *) realloc (*strptr,
- strleng + MB_LEN_MAX);
- if (newstr == NULL)
- {
- /* c can't have `a' flag, only `m'. */
- done = EOF;
- goto errout;
- }
- else
- {
- *strptr = newstr;
- str = newstr + strleng;
- strsize = strleng + MB_LEN_MAX;
- }
+ /* c can't have `a' flag, only `m'. */
+ done = EOF;
+ goto errout;
}
else
{
@@ -874,21 +862,9 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
str = (char *) realloc (*strptr, newsize);
if (str == NULL)
{
- /* Can't allocate that much. Last-ditch
- effort. */
- str = (char *) realloc (*strptr, strsize + 1);
- if (str == NULL)
- {
- /* c can't have `a' flag, only `m'. */
- done = EOF;
- goto errout;
- }
- else
- {
- *strptr = (char *) str;
- str += strsize;
- ++strsize;
- }
+ /* c can't have `a' flag, only `m'. */
+ done = EOF;
+ goto errout;
}
else
{
@@ -949,23 +925,9 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
sizeof (wchar_t));
if (wstr == NULL)
{
- /* Can't allocate that much. Last-ditch effort. */
- wstr = (wchar_t *)
- __libc_reallocarray (*strptr, strsize + 1,
- sizeof (wchar_t));
- if (wstr == NULL)
- {
- /* C or lc can't have `a' flag, only `m'
- flag. */
- done = EOF;
- goto errout;
- }
- else
- {
- *strptr = (char *) wstr;
- wstr += strsize;
- ++strsize;
- }
+ /* C or lc can't have `a' flag, only `m' flag. */
+ done = EOF;
+ goto errout;
}
else
{
@@ -1004,22 +966,9 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
sizeof (wchar_t));
if (wstr == NULL)
{
- /* Can't allocate that much. Last-ditch effort. */
- wstr = (wchar_t *)
- __libc_reallocarray (*strptr, strsize + 1,
- sizeof (wchar_t));
- if (wstr == NULL)
- {
- /* C or lc can't have `a' flag, only `m' flag. */
- done = EOF;
- goto errout;
- }
- else
- {
- *strptr = (char *) wstr;
- wstr += strsize;
- ++strsize;
- }
+ /* C or lc can't have `a' flag, only `m' flag. */
+ done = EOF;
+ goto errout;
}
else
{
@@ -1120,31 +1069,18 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
newstr = (char *) realloc (*strptr, strsize * 2);
if (newstr == NULL)
{
- /* Can't allocate that much. Last-ditch
- effort. */
- newstr = (char *) realloc (*strptr,
- strleng + MB_LEN_MAX);
- if (newstr == NULL)
- {
- if (flags & POSIX_MALLOC)
- {
- done = EOF;
- goto errout;
- }
- /* We lose. Oh well. Terminate the
- string and stop converting,
- so at least we don't skip any input. */
- ((char *) (*strptr))[strleng] = '\0';
- strptr = NULL;
- ++done;
- conv_error ();
- }
- else
+ if (flags & POSIX_MALLOC)
{
- *strptr = newstr;
- str = newstr + strleng;
- strsize = strleng + MB_LEN_MAX;
+ done = EOF;
+ goto errout;
}
+ /* We lose. Oh well. Terminate the
+ string and stop converting,
+ so at least we don't skip any input. */
+ ((char *) (*strptr))[strleng] = '\0';
+ strptr = NULL;
+ ++done;
+ conv_error ();
}
else
{
@@ -1176,30 +1112,18 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
str = (char *) realloc (*strptr, newsize);
if (str == NULL)
{
- /* Can't allocate that much. Last-ditch
- effort. */
- str = (char *) realloc (*strptr, strsize + 1);
- if (str == NULL)
- {
- if (flags & POSIX_MALLOC)
- {
- done = EOF;
- goto errout;
- }
- /* We lose. Oh well. Terminate the
- string and stop converting,
- so at least we don't skip any input. */
- ((char *) (*strptr))[strsize - 1] = '\0';
- strptr = NULL;
- ++done;
- conv_error ();
- }
- else
+ if (flags & POSIX_MALLOC)
{
- *strptr = (char *) str;
- str += strsize;
- ++strsize;
+ done = EOF;
+ goto errout;
}
+ /* We lose. Oh well. Terminate the
+ string and stop converting,
+ so at least we don't skip any input. */
+ ((char *) (*strptr))[strsize - 1] = '\0';
+ strptr = NULL;
+ ++done;
+ conv_error ();
}
else
{
@@ -1309,32 +1233,18 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
(*strptr, newsize, sizeof (wchar_t));
if (wstr == NULL)
{
- /* Can't allocate that much. Last-ditch
- effort. */
- wstr = (wchar_t *)
- __libc_reallocarray (*strptr, strsize + 1,
- sizeof (wchar_t));
- if (wstr == NULL)
+ if (flags & POSIX_MALLOC)
{
- if (flags & POSIX_MALLOC)
- {
- done = EOF;
- goto errout;
- }
- /* We lose. Oh well. Terminate the string
- and stop converting, so at least we don't
- skip any input. */
- ((wchar_t *) (*strptr))[strsize - 1] = L'\0';
- strptr = NULL;
- ++done;
- conv_error ();
- }
- else
- {
- *strptr = (char *) wstr;
- wstr += strsize;
- ++strsize;
+ done = EOF;
+ goto errout;
}
+ /* We lose. Oh well. Terminate the string
+ and stop converting, so at least we don't
+ skip any input. */
+ ((wchar_t *) (*strptr))[strsize - 1] = L'\0';
+ strptr = NULL;
+ ++done;
+ conv_error ();
}
else
{
@@ -1387,31 +1297,18 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
sizeof (wchar_t));
if (wstr == NULL)
{
- /* Can't allocate that much. Last-ditch effort. */
- wstr = (wchar_t *)
- __libc_reallocarray (*strptr, strsize + 1,
- sizeof (wchar_t));
- if (wstr == NULL)
- {
- if (flags & POSIX_MALLOC)
- {
- done = EOF;
- goto errout;
- }
- /* We lose. Oh well. Terminate the
- string and stop converting, so at
- least we don't skip any input. */
- ((wchar_t *) (*strptr))[strsize - 1] = L'\0';
- strptr = NULL;
- ++done;
- conv_error ();
- }
- else
+ if (flags & POSIX_MALLOC)
{
- *strptr = (char *) wstr;
- wstr += strsize;
- ++strsize;
+ done = EOF;
+ goto errout;
}
+ /* We lose. Oh well. Terminate the
+ string and stop converting, so at
+ least we don't skip any input. */
+ ((wchar_t *) (*strptr))[strsize - 1] = L'\0';
+ strptr = NULL;
+ ++done;
+ conv_error ();
}
else
{
@@ -2804,32 +2701,18 @@ digits_extended_fail:
(*strptr, newsize, sizeof (wchar_t));
if (wstr == NULL)
{
- /* Can't allocate that much. Last-ditch
- effort. */
- wstr = (wchar_t *)
- __libc_reallocarray (*strptr, strsize + 1,
- sizeof (wchar_t));
- if (wstr == NULL)
- {
- if (flags & POSIX_MALLOC)
- {
- done = EOF;
- goto errout;
- }
- /* We lose. Oh well. Terminate the string
- and stop converting, so at least we don't
- skip any input. */
- ((wchar_t *) (*strptr))[strsize - 1] = L'\0';
- strptr = NULL;
- ++done;
- conv_error ();
- }
- else
+ if (flags & POSIX_MALLOC)
{
- *strptr = (char *) wstr;
- wstr += strsize;
- ++strsize;
+ done = EOF;
+ goto errout;
}
+ /* We lose. Oh well. Terminate the string
+ and stop converting, so at least we don't
+ skip any input. */
+ ((wchar_t *) (*strptr))[strsize - 1] = L'\0';
+ strptr = NULL;
+ ++done;
+ conv_error ();
}
else
{
@@ -2890,32 +2773,18 @@ digits_extended_fail:
(*strptr, newsize, sizeof (wchar_t));
if (wstr == NULL)
{
- /* Can't allocate that much. Last-ditch
- effort. */
- wstr = (wchar_t *)
- __libc_reallocarray (*strptr, strsize + 1,
- sizeof (wchar_t));
- if (wstr == NULL)
- {
- if (flags & POSIX_MALLOC)
- {
- done = EOF;
- goto errout;
- }
- /* We lose. Oh well. Terminate the
- string and stop converting,
- so at least we don't skip any input. */
- ((wchar_t *) (*strptr))[strsize - 1] = L'\0';
- strptr = NULL;
- ++done;
- conv_error ();
- }
- else
+ if (flags & POSIX_MALLOC)
{
- *strptr = (char *) wstr;
- wstr += strsize;
- ++strsize;
+ done = EOF;
+ goto errout;
}
+ /* We lose. Oh well. Terminate the
+ string and stop converting,
+ so at least we don't skip any input. */
+ ((wchar_t *) (*strptr))[strsize - 1] = L'\0';
+ strptr = NULL;
+ ++done;
+ conv_error ();
}
else
{
@@ -3039,31 +2908,18 @@ digits_extended_fail:
newstr = (char *) realloc (*strptr, 2 * strsize);
if (newstr == NULL)
{
- /* Can't allocate that much. Last-ditch
- effort. */
- newstr = (char *) realloc (*strptr,
- strleng + MB_LEN_MAX);
- if (newstr == NULL)
- {
- if (flags & POSIX_MALLOC)
- {
- done = EOF;
- goto errout;
- }
- /* We lose. Oh well. Terminate the string
- and stop converting, so at least we don't
- skip any input. */
- ((char *) (*strptr))[strleng] = '\0';
- strptr = NULL;
- ++done;
- conv_error ();
- }
- else
+ if (flags & POSIX_MALLOC)
{
- *strptr = newstr;
- str = newstr + strleng;
- strsize = strleng + MB_LEN_MAX;
+ done = EOF;
+ goto errout;
}
+ /* We lose. Oh well. Terminate the string
+ and stop converting, so at least we don't
+ skip any input. */
+ ((char *) (*strptr))[strleng] = '\0';
+ strptr = NULL;
+ ++done;
+ conv_error ();
}
else
{
@@ -3102,17 +2958,9 @@ digits_extended_fail:
/* Enlarge the buffer. */
size_t newsize = grow_to_fit (strsize, width);
- allocagain:
str = (char *) realloc (*strptr, newsize);
if (str == NULL)
{
- /* Can't allocate that much. Last-ditch
- effort. */
- if (newsize > strsize + 1)
- {
- newsize = strsize + 1;
- goto allocagain;
- }
if (flags & POSIX_MALLOC)
{
done = EOF;
--
2.55.0
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