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Message-Id: <20260203103000.20206-7-david.laight.linux@gmail.com>
Date: Tue, 3 Feb 2026 10:29:54 +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 06/12] tools/nolibc/printf: Add support for left alignment and %[tzLq]d"
From: David Laight <david.laight.linux@...il.com>
Use a single 'flags' variable to hold both format flags and length modifiers.
Use (1u << (c & 31)) for the flag bits to reduce code complexity.
Add support for left justifying fields.
Add support for length modifiers 't' and 'z' (both long) and 'q' and 'L'
(both long long).
Unconditionall generate the signed values (for %d) to remove a second
set of checks for the size.
Use 'signed int' for the lengths to make the pad test simpler.
Signed-off-by: David Laight <david.laight.linux@...il.com>
---
tools/include/nolibc/stdio.h | 88 ++++++++++++++++++++----------------
1 file changed, 50 insertions(+), 38 deletions(-)
diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
index 164d2384978e..1ce4d357a802 100644
--- a/tools/include/nolibc/stdio.h
+++ b/tools/include/nolibc/stdio.h
@@ -240,20 +240,20 @@ char *fgets(char *s, int size, FILE *stream)
}
-/* minimal printf(). It supports the following formats:
- * - %[l*]{d,u,c,x,p}
- * - %s
- * - unknown modifiers are ignored.
+/* simple printf(). It supports the following formats:
+ * - %[-][width][{l,t,z,ll,L,j,q}]{d,u,c,x,p,s,m}
+ * - %%
+ * - invalid formats are copied to the output buffer
*/
typedef int (*__nolibc_printf_cb)(void *state, const char *buf, size_t size);
+#define __PF_FLAG(c) (1u << ((c) & 0x1f))
static __attribute__((unused, format(printf, 3, 0)))
int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list args)
{
- char lpref, c;
- unsigned long long v;
- unsigned int written, width;
- size_t len;
+ char c;
+ int len, written, width;
+ unsigned int flags;
char tmpbuf[21];
const char *outstr;
@@ -265,6 +265,7 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
break;
width = 0;
+ flags = 0;
if (c != '%') {
while (*fmt && *fmt != '%')
fmt++;
@@ -274,6 +275,13 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
c = *fmt++;
+ /* Flag characters */
+ for (; c >= 0x20 && c <= 0x3f; c = *fmt++) {
+ if ((__PF_FLAG(c) & (__PF_FLAG('-'))) == 0)
+ break;
+ flags |= __PF_FLAG(c);
+ }
+
/* width */
while (c >= '0' && c <= '9') {
width *= 10;
@@ -282,41 +290,34 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
c = *fmt++;
}
- /* Length modifiers */
- if (c == 'l') {
- lpref = 1;
- c = *fmt++;
- if (c == 'l') {
- lpref = 2;
+ /* Length modifiers are lower case except 'L' which is the same a 'q' */
+ if ((c >= 'a' && c <= 'z') || (c == 'L' && (c = 'q'))) {
+ if (__PF_FLAG(c) & (__PF_FLAG('l') | __PF_FLAG('t') | __PF_FLAG('z') |
+ __PF_FLAG('j') | __PF_FLAG('q'))) {
+ if (c == 'l' && fmt[0] == 'l') {
+ fmt++;
+ c = 'q';
+ }
+ /* These all miss "# -0+" */
+ flags |= __PF_FLAG(c);
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') {
+ unsigned long long v;
+ long long signed_v;
char *out = tmpbuf;
- if (c == 'p')
+ if ((c == 'p') || (flags & (__PF_FLAG('l') | __PF_FLAG('t') | __PF_FLAG('z')))) {
v = va_arg(args, unsigned long);
- else if (lpref) {
- if (lpref > 1)
- v = va_arg(args, unsigned long long);
- else
- v = va_arg(args, unsigned long);
- } else
+ signed_v = (long)v;
+ } else if (flags & (__PF_FLAG('j') | __PF_FLAG('q'))) {
+ v = va_arg(args, unsigned long long);
+ signed_v = v;
+ } else {
v = va_arg(args, unsigned int);
-
- if (c == 'd') {
- /* sign-extend the value */
- if (lpref == 0)
- v = (long long)(int)v;
- else if (lpref == 1)
- v = (long long)(long)v;
+ signed_v = (int)v;
}
switch (c) {
@@ -325,7 +326,7 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
out[1] = 0;
break;
case 'd':
- i64toa_r(v, out);
+ i64toa_r(signed_v, out);
break;
case 'u':
u64toa_r(v, out);
@@ -366,14 +367,24 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
written += len;
- while (width > len) {
- unsigned int pad_len = ((width - len - 1) & 15) + 1;
+ /* An OPTIMIZER_HIDE_VAR() seems to stop gcc back-merging this
+ * code into one of the conditionals above.
+ */
+ __asm__ volatile("" : "=r"(len) : "0"(len));
+
+ /* Output 'left pad', 'value' then 'right pad'. */
+ flags &= __PF_FLAG('-');
+ width -= len;
+ if (flags && cb(state, outstr, len) != 0)
+ return -1;
+ while (width > 0) {
+ int pad_len = ((width - 1) & 15) + 1;
width -= pad_len;
written += pad_len;
if (cb(state, " ", pad_len) != 0)
return -1;
}
- if (cb(state, outstr, len) != 0)
+ if (!flags && cb(state, outstr, len) != 0)
return -1;
}
@@ -382,6 +393,7 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
return written;
}
+#undef _PF_FLAG
struct __nolibc_fprintf_cb_state {
FILE *stream;
--
2.39.5
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