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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-485237dd017sm63621855e9.2.2026.03.08.04.37.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Mar 2026 04:37:54 -0700 (PDT) From: david.laight.linux@gmail.com To: Willy Tarreau , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , linux-kernel@vger.kernel.org, Cheng Li Cc: David Laight Subject: [PATCH v5 next 08/17] tools/nolibc/printf: Use bit-masks to hold requested flag, length and conversion chars Date: Sun, 8 Mar 2026 11:37:33 +0000 Message-Id: <20260308113742.12649-9-david.laight.linux@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260308113742.12649-1-david.laight.linux@gmail.com> References: <20260308113742.12649-1-david.laight.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: David Laight Use flags bits (1u << (ch & 31)) for the flags, length modifiers, and conversion specifiers. This makes it easy to test for multiple values at once. Detect the conversion flags " #+-0" although they are currently all ignored. Unconditionally generate the signed values (for %d) to remove a second set of checks for the size. Separate out the formatting of single characters from numbers. Output the sign for negative values then negate and treat as unsigned. Acked-by: Willy Tarreau Signed-off-by: David Laight --- Unchanged for v5. Changes for v4: - Move the support for length modifiers t, j, q, L and formats i and X to the next patch. - Convert ll to j (not q) since q isn't added until the next patch. Changes for v3: - Patch 6 in v2. - Move all the variable definitions to the top of the function. The loop body is a bit long to hide definitions at its top. - Avoid -Wtype-limits validating format characters. - Include changes to the selftests. Changes for v2: - Use #defines to make the code a lot more readable. - Include the changes from the old patch 10 that used masks for the conversion specifiers. - Detect all the valid flag characters even though they are not implemented. - Support for left justifying field is moved to patch 7. tools/include/nolibc/stdio.h | 157 ++++++++++++++++++++++++----------- 1 file changed, 108 insertions(+), 49 deletions(-) diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h index 710a4bce5e81..1c2b2cf9a1f3 100644 --- a/tools/include/nolibc/stdio.h +++ b/tools/include/nolibc/stdio.h @@ -291,10 +291,14 @@ int fseek(FILE *stream, long offset, int whence) } -/* minimal printf(). It supports the following formats: - * - %[l*]{d,u,c,x,p} - * - %s - * - unknown modifiers are ignored. +/* printf(). Supports the following integer and string formats. + * - %[#-+ 0][width][{l,ll,j}]{c,d,u,x,p,s,m,%} + * - %% generates a single % + * - %m outputs strerror(errno). + * - The modifiers [#-+ 0] are currently ignored. + * - No support for precision or variable widths. + * - No support for floating point or wide characters. + * - Invalid formats are copied to the output buffer. * * Called by vfprintf() and snprintf() to do the actual formatting. * The callers provide a callback function to save the formatted data. @@ -305,15 +309,43 @@ int fseek(FILE *stream, long offset, int whence) * - with (NULL, 0) at the end of the __nolibc_printf. * If the callback returns non-zero __nolibc_printf() immediately returns -1. */ + typedef int (*__nolibc_printf_cb)(void *state, const char *buf, size_t size); +/* This code uses 'flag' variables that are indexed by the low 6 bits + * of characters to optimise checks for multiple characters. + * + * _NOLIBC_PF_FLAGS_CONTAIN(flags, 'a', 'b'. ...) + * returns non-zero if the bit for any of the specified characters is set. + * + * _NOLIBC_PF_CHAR_IS_ONE_OF(ch, 'a', 'b'. ...) + * returns the flag bit for ch if it is one of the specified characters. + * All the characters must be in the same 32 character block (non-alphabetic, + * upper case, or lower case) of the ASCII character set. + */ +#define _NOLIBC_PF_FLAG(ch) (1u << ((ch) & 0x1f)) +#define _NOLIBC_PF_FLAG_NZ(ch) ((ch) ? _NOLIBC_PF_FLAG(ch) : 0) +#define _NOLIBC_PF_FLAG8(cmp_1, cmp_2, cmp_3, cmp_4, cmp_5, cmp_6, cmp_7, cmp_8, ...) \ + (_NOLIBC_PF_FLAG_NZ(cmp_1) | _NOLIBC_PF_FLAG_NZ(cmp_2) | \ + _NOLIBC_PF_FLAG_NZ(cmp_3) | _NOLIBC_PF_FLAG_NZ(cmp_4) | \ + _NOLIBC_PF_FLAG_NZ(cmp_5) | _NOLIBC_PF_FLAG_NZ(cmp_6) | \ + _NOLIBC_PF_FLAG_NZ(cmp_7) | _NOLIBC_PF_FLAG_NZ(cmp_8)) +#define _NOLIBC_PF_FLAGS_CONTAIN(flags, ...) \ + ((flags) & _NOLIBC_PF_FLAG8(__VA_ARGS__, 0, 0, 0, 0, 0, 0, 0)) +#define _NOLIBC_PF_CHAR_IS_ONE_OF(ch, cmp_1, ...) \ + ((unsigned int)(ch) - (cmp_1 & 0xe0) > 0x1f ? 0 : \ + _NOLIBC_PF_FLAGS_CONTAIN(_NOLIBC_PF_FLAG(ch), cmp_1, __VA_ARGS__)) + static __attribute__((unused, format(printf, 3, 0))) int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list args) { - char lpref, ch; + char ch; unsigned long long v; + long long signed_v; int written, width, len; + unsigned int flags, ch_flag; char outbuf[21]; + char *out; const char *outstr; written = 0; @@ -324,6 +356,7 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list break; width = 0; + flags = 0; if (ch != '%') { while (*fmt && *fmt != '%') fmt++; @@ -334,7 +367,14 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list /* we're in a format sequence */ - ch = *fmt++; + /* Conversion flag characters */ + while (1) { + ch = *fmt++; + ch_flag = _NOLIBC_PF_CHAR_IS_ONE_OF(ch, ' ', '#', '+', '-', '0'); + if (!ch_flag) + break; + flags |= ch_flag; + } /* width */ while (ch >= '0' && ch <= '9') { @@ -344,62 +384,78 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list ch = *fmt++; } - /* Length modifiers */ - if (ch == 'l') { - lpref = 1; - ch = *fmt++; - if (ch == 'l') { - lpref = 2; - ch = *fmt++; + /* Length modifier. + * They miss the conversion flags characters " #+-0" so can go into flags. + * Change ll to j (both always 64bits). + */ + ch_flag = _NOLIBC_PF_CHAR_IS_ONE_OF(ch, 'l', 'j'); + if (ch_flag != 0) { + if (ch == 'l' && fmt[0] == 'l') { + fmt++; + ch_flag = _NOLIBC_PF_FLAG('j'); } - } else if (ch == 'j') { - /* intmax_t is long long */ - lpref = 2; + flags |= ch_flag; ch = *fmt++; - } else { - lpref = 0; } - if (ch == 'c' || ch == 'd' || ch == 'u' || ch == 'x' || ch == 'p') { - char *out = outbuf; + /* Conversion specifiers. */ - if (ch == 'p') + /* Numeric and pointer conversion specifiers. + * + * Use an explicit bound check (rather than _NOLIBC_PF_CHAR_IS_ONE_OF()) + * so ch_flag can be used later. + */ + ch_flag = _NOLIBC_PF_FLAG(ch); + if ((ch >= 'a' && ch <= 'z') && + _NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'c', 'd', 'u', 'x', 'p')) { + /* 'long' is needed for pointer conversions and ltz lengths. + * A single test can be used provided 'p' (the same bit as '0') + * is masked from flags. + */ + if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag | (flags & ~_NOLIBC_PF_FLAG('p')), + 'p', 'l')) { 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 (_NOLIBC_PF_FLAGS_CONTAIN(flags, 'j')) { + v = va_arg(args, unsigned long long); + signed_v = v; + } else { v = va_arg(args, unsigned int); + signed_v = (int)v; + } - if (ch == 'd') { - /* sign-extend the value */ - if (lpref == 0) - v = (long long)(int)v; - else if (lpref == 1) - v = (long long)(long)v; + if (ch == 'c') { + /* "%c" - single character. */ + outbuf[0] = v; + len = 1; + outstr = outbuf; + goto do_output; } - switch (ch) { - case 'c': - out[0] = v; - out[1] = 0; - break; - case 'd': - i64toa_r(v, out); - break; - case 'u': + out = outbuf; + + if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'd')) { + /* "%d" and "%i" - signed decimal numbers. */ + if (signed_v < 0) { + *out++ = '-'; + v = -(signed_v + 1); + v++; + } + } + + /* Convert the number to ascii in the required base. */ + if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'd', 'u')) { + /* Base 10 */ u64toa_r(v, out); - break; - case 'p': - *(out++) = '0'; - *(out++) = 'x'; - __nolibc_fallthrough; - default: /* 'x' and 'p' above */ + } else { + /* Base 16 */ + if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'p')) { + *(out++) = '0'; + *(out++) = 'x'; + } u64toh_r(v, out); - break; } + outstr = outbuf; goto do_strlen_output; } @@ -442,6 +498,9 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list do_output: written += len; + /* Stop gcc back-merging this code into one of the conditionals above. */ + _NOLIBC_OPTIMIZER_HIDE_VAR(len); + width -= len; while (width > 0) { /* Output pad in 16 byte blocks with the small block first. */ -- 2.39.5