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Message-Id: <20260203103000.20206-6-david.laight.linux@gmail.com>
Date: Tue, 3 Feb 2026 10:29:53 +0000
From: david.laight.linux@...il.com
To: Willy Tarreau <w@....eu>,
Thomas Weißschuh <linux@...ssschuh.net>,
linux-kernel@...r.kernel.org,
Cheng Li <lechain@...il.com>
Cc: David Laight <david.laight.linux@...il.com>
Subject: [PATCH next 05/12] tools/nolibc/printf: Simplify __nolibc_printf()
From: David Laight <david.laight.linux@...il.com>
Move the check for the length modifiers into the format processing
between the field width and conversion specifier.
This lets the loop be simplified and a 'fast scan' for a format start
used.
If an error is detected (eg an invalid conversion specifier) then
copy the invalid format to the output buffer.
Reduces code size by about 10% on x86-64.
Signed-off-by: David Laight <david.laight.linux@...il.com>
---
tools/include/nolibc/stdio.h | 100 +++++++++++++++++------------------
1 file changed, 50 insertions(+), 50 deletions(-)
diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
index 52cb516ea3db..164d2384978e 100644
--- a/tools/include/nolibc/stdio.h
+++ b/tools/include/nolibc/stdio.h
@@ -250,28 +250,52 @@ typedef int (*__nolibc_printf_cb)(void *state, const char *buf, size_t size);
static __attribute__((unused, format(printf, 3, 0)))
int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list args)
{
- char escape, lpref, c;
+ char lpref, c;
unsigned long long v;
unsigned int written, width;
- size_t len, ofs;
+ size_t len;
char tmpbuf[21];
const char *outstr;
- written = ofs = escape = lpref = 0;
+ written = 0;
while (1) {
- c = fmt[ofs++];
+ outstr = fmt;
+ c = *fmt++;
+ if (!c)
+ break;
+
width = 0;
+ if (c != '%') {
+ while (*fmt && *fmt != '%')
+ fmt++;
+ len = fmt - outstr;
+ } else {
+ /* we're in a format sequence */
- if (escape) {
- /* we're in an escape sequence, ofs == 1 */
- escape = 0;
+ c = *fmt++;
/* width */
while (c >= '0' && c <= '9') {
width *= 10;
width += c - '0';
- c = fmt[ofs++];
+ c = *fmt++;
+ }
+
+ /* Length modifiers */
+ if (c == 'l') {
+ lpref = 1;
+ c = *fmt++;
+ if (c == 'l') {
+ lpref = 2;
+ c = *fmt++;
+ }
+ } else if (c == 'j') {
+ /* intmax_t is long long */
+ lpref = 2;
+ c = *fmt++;
+ } else {
+ lpref = 0;
}
if (c == 'c' || c == 'd' || c == 'u' || c == 'x' || c == 'p') {
@@ -327,54 +351,30 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
#else
outstr = strerror(errno);
#endif /* NOLIBC_IGNORE_ERRNO */
- }
- else if (c == '%') {
- /* queue it verbatim */
- continue;
- }
- else {
- /* modifiers or final 0 */
- if (c == 'l') {
- /* long format prefix, maintain the escape */
- lpref++;
- } else if (c == 'j') {
- lpref = 2;
- }
- escape = 1;
- goto do_escape;
+ } else {
+ if (c != '%')
+ /* Invalid format, output the format string */
+ fmt = outstr + 1;
+ /* %% is documented as a 'conversion specifier'.
+ * Any flags, precision or length modifier are ignored.
+ */
+ width = 0;
+ outstr = "%";
}
len = strlen(outstr);
- goto flush_str;
}
- /* not an escape sequence */
- if (c == 0 || c == '%') {
- /* flush pending data on escape or end */
- escape = 1;
- lpref = 0;
- outstr = fmt;
- len = ofs - 1;
- flush_str:
- while (width > len) {
- unsigned int pad_len = ((width - len - 1) & 15) + 1;
- width -= pad_len;
- written += pad_len;
- if (cb(state, " ", pad_len) != 0)
- return -1;
- }
- if (cb(state, outstr, len) != 0)
- return -1;
+ written += len;
- written += len;
- do_escape:
- if (c == 0)
- break;
- fmt += ofs;
- ofs = 0;
- continue;
+ while (width > len) {
+ unsigned int pad_len = ((width - len - 1) & 15) + 1;
+ width -= pad_len;
+ written += pad_len;
+ if (cb(state, " ", pad_len) != 0)
+ return -1;
}
-
- /* literal char, just queue it */
+ if (cb(state, outstr, len) != 0)
+ return -1;
}
if (cb(state, NULL, 0) != 0)
--
2.39.5
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