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GET /api/patches/2237933/?format=api
{ "id": 2237933, "url": "http://patchwork.ozlabs.org/api/patches/2237933/?format=api", "web_url": "http://patchwork.ozlabs.org/project/glibc/patch/20260513163046.2150310-1-marocketbd@gmail.com/", "project": { "id": 41, "url": "http://patchwork.ozlabs.org/api/projects/41/?format=api", "name": "GNU C Library", "link_name": "glibc", "list_id": "libc-alpha.sourceware.org", "list_email": "libc-alpha@sourceware.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260513163046.2150310-1-marocketbd@gmail.com>", "list_archive_url": null, "date": "2026-05-13T16:30:46", "name": "stdio-common: Optimize scanf %ms series array expansion", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "c5a6f78d0cb01e5c790b9bc81241b9c3d80ceed6", "submitter": { "id": 92898, "url": "http://patchwork.ozlabs.org/api/people/92898/?format=api", "name": "Rocket Ma", "email": "marocketbd@gmail.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/glibc/patch/20260513163046.2150310-1-marocketbd@gmail.com/mbox/", "series": [ { "id": 504186, "url": "http://patchwork.ozlabs.org/api/series/504186/?format=api", "web_url": "http://patchwork.ozlabs.org/project/glibc/list/?series=504186", "date": "2026-05-13T16:30:46", "name": "stdio-common: Optimize scanf %ms series array expansion", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/504186/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2237933/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2237933/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "libc-alpha@sourceware.org" ], "Delivered-To": [ "patchwork-incoming@legolas.ozlabs.org", "libc-alpha@sourceware.org" ], "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=KrGZ/hCY;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=38.145.34.32; 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Instead of\nalways expanding exponentially, try to expand array to the exact size\nuser requested when `user_size < current_size * 2`.\n\nSigned-off-by: Rocket Ma <marocketbd@gmail.com>\n---\nThis is a deferred patch from `[v5,3/3] stdio-common: Optimize %ms expansion\nfor best fit'[1].\n\n[1]: https://inbox.sourceware.org/libc-alpha/e48ff256-40b9-4fc4-9898-8bce0e6b4651@redhat.com/\n---\n stdio-common/vfscanf-internal.c | 63 ++++++++++++++++++++++-----------\n 1 file changed, 42 insertions(+), 21 deletions(-)", "diff": "diff --git a/stdio-common/vfscanf-internal.c b/stdio-common/vfscanf-internal.c\nindex 3d11ac261e..8eec294a98 100644\n--- a/stdio-common/vfscanf-internal.c\n+++ b/stdio-common/vfscanf-internal.c\n@@ -265,6 +265,17 @@ char_buffer_add (struct char_buffer *buffer, CHAR_T ch)\n *buffer->current++ = ch;\n }\n \n+/* Calculate the result size of expanded char array in %ms, %mS,\n+ %m[ or %lm[. */\n+static __always_inline size_t\n+grow_to_fit (size_t oldsize, int need)\n+{\n+ if (need < 0 || oldsize < need)\n+ return oldsize * 2;\n+ /* oldsize >= need: grow requested capacity and 1 byte for `\\0' */\n+ return oldsize + need + 1;\n+}\n+\n /* Read formatted input from S according to the format string\n FORMAT, using the argument list in ARG.\n Return the number of assignments made, or -1 for an input error. */\n@@ -804,7 +815,8 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,\n \t\t && *strptr + strsize - str <= MB_LEN_MAX)\n \t\t {\n \t\t /* We have to enlarge the buffer if the `m' flag\n-\t\t\t was given. */\n+\t\t\t was given. And we may not expand str by width\n+\t\t\t as the wcrtomb may return various bytes */\n \t\t size_t strleng = str - *strptr;\n \t\t char *newstr;\n \n@@ -1098,7 +1110,8 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,\n \t\t\t&& *strptr + strsize - str <= MB_LEN_MAX)\n \t\t {\n \t\t\t/* We have to enlarge the buffer if the `a' or `m'\n-\t\t\t flag was given. */\n+\t\t\t flag was given. And we may not expand str by\n+\t\t\t width as the wcrtomb may return various bytes */\n \t\t\tsize_t strleng = str - *strptr;\n \t\t\tchar *newstr;\n \n@@ -1156,7 +1169,9 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,\n \t\t\t && (char *) str == *strptr + strsize)\n \t\t\t{\n \t\t\t /* Enlarge the buffer. */\n-\t\t\t str = (char *) realloc (*strptr, 2 * strsize);\n+\t\t\t size_t newsize = grow_to_fit (strsize, width);\n+\n+\t\t\t str = (char *) realloc (*strptr, newsize);\n \t\t\t if (str == NULL)\n \t\t\t {\n \t\t\t /* Can't allocate that much. Last-ditch\n@@ -1188,7 +1203,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,\n \t\t\t {\n \t\t\t *strptr = (char *) str;\n \t\t\t str += strsize;\n-\t\t\t strsize *= 2;\n+\t\t\t strsize = newsize;\n \t\t\t }\n \t\t\t}\n \t\t }\n@@ -1286,9 +1301,10 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,\n \t\t\t&& wstr == (wchar_t *) *strptr + strsize)\n \t\t {\n \t\t\t/* Enlarge the buffer. */\n-\t\t\twstr = (wchar_t *) realloc (*strptr,\n-\t\t\t\t\t\t (2 * strsize)\n-\t\t\t\t\t\t * sizeof (wchar_t));\n+\t\t\tsize_t newsize = grow_to_fit (strsize, width);\n+\n+\t\t\twstr = (wchar_t *) realloc (\n+\t\t\t *strptr, newsize * sizeof (wchar_t));\n \t\t\tif (wstr == NULL)\n \t\t\t {\n \t\t\t /* Can't allocate that much. Last-ditch\n@@ -1322,7 +1338,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,\n \t\t\t {\n \t\t\t *strptr = (char *) wstr;\n \t\t\t wstr += strsize;\n-\t\t\t strsize *= 2;\n+\t\t\t strsize = newsize;\n \t\t\t }\n \t\t }\n \t\t }\n@@ -1362,9 +1378,10 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,\n \t\t && wstr == (wchar_t *) *strptr + strsize)\n \t\t {\n \t\t /* Enlarge the buffer. */\n+\t\t size_t newsize = grow_to_fit (strsize, width);\n+\n \t\t wstr = (wchar_t *) realloc (*strptr,\n-\t\t\t\t\t\t (2 * strsize\n-\t\t\t\t\t\t * sizeof (wchar_t)));\n+\t\t\t\t\t\t newsize * sizeof (wchar_t));\n \t\t if (wstr == NULL)\n \t\t\t{\n \t\t\t /* Can't allocate that much. Last-ditch effort. */\n@@ -1397,7 +1414,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,\n \t\t\t{\n \t\t\t *strptr = (char *) wstr;\n \t\t\t wstr += strsize;\n-\t\t\t strsize *= 2;\n+\t\t\t strsize = newsize;\n \t\t\t}\n \t\t }\n \t\t}\n@@ -2754,9 +2771,10 @@ digits_extended_fail:\n \t\t\t && wstr == (wchar_t *) *strptr + strsize)\n \t\t\t{\n \t\t\t /* Enlarge the buffer. */\n-\t\t\t wstr = (wchar_t *) realloc (*strptr,\n-\t\t\t\t\t\t (2 * strsize)\n-\t\t\t\t\t\t * sizeof (wchar_t));\n+\t\t\t size_t newsize = grow_to_fit (strsize, width);\n+\n+\t\t\t wstr = (wchar_t *) realloc (\n+\t\t\t *strptr, newsize * sizeof (wchar_t));\n \t\t\t if (wstr == NULL)\n \t\t\t {\n \t\t\t /* Can't allocate that much. Last-ditch\n@@ -2790,7 +2808,7 @@ digits_extended_fail:\n \t\t\t {\n \t\t\t *strptr = (char *) wstr;\n \t\t\t wstr += strsize;\n-\t\t\t strsize *= 2;\n+\t\t\t strsize = newsize;\n \t\t\t }\n \t\t\t}\n \t\t }\n@@ -2839,9 +2857,10 @@ digits_extended_fail:\n \t\t\t && wstr == (wchar_t *) *strptr + strsize)\n \t\t\t{\n \t\t\t /* Enlarge the buffer. */\n-\t\t\t wstr = (wchar_t *) realloc (*strptr,\n-\t\t\t\t\t\t (2 * strsize\n-\t\t\t\t\t\t * sizeof (wchar_t)));\n+\t\t\t size_t newsize = grow_to_fit (strsize, width);\n+\n+\t\t\t wstr = (wchar_t *) realloc (\n+\t\t\t *strptr, newsize * sizeof (wchar_t));\n \t\t\t if (wstr == NULL)\n \t\t\t {\n \t\t\t /* Can't allocate that much. Last-ditch\n@@ -2875,7 +2894,7 @@ digits_extended_fail:\n \t\t\t {\n \t\t\t *strptr = (char *) wstr;\n \t\t\t wstr += strsize;\n-\t\t\t strsize *= 2;\n+\t\t\t strsize = newsize;\n \t\t\t }\n \t\t\t}\n \t\t }\n@@ -2983,7 +3002,9 @@ digits_extended_fail:\n \t\t if ((flags & MALLOC)\n \t\t\t && *strptr + strsize - str <= MB_LEN_MAX)\n \t\t\t{\n-\t\t\t /* Enlarge the buffer. */\n+\t\t\t /* Enlarge the buffer. And we may not\n+\t\t\t expand str by width as the wcrtomb may\n+\t\t\t return various bytes */\n \t\t\t size_t strleng = str - *strptr;\n \t\t\t char *newstr;\n \n@@ -3051,7 +3072,7 @@ digits_extended_fail:\n \t\t\t && (char *) str == *strptr + strsize)\n \t\t\t{\n \t\t\t /* Enlarge the buffer. */\n-\t\t\t size_t newsize = 2 * strsize;\n+\t\t\t size_t newsize = grow_to_fit (strsize, width);\n \n \t\t\tallocagain:\n \t\t\t str = (char *) realloc (*strptr, newsize);\n", "prefixes": [] }