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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435e10edf62sm55940729f8f.13.2026.02.03.02.30.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Feb 2026 02:30:13 -0800 (PST) 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 next 08/12] tools/nolibc/printf: use bit-match to detect valid conversion characters Date: Tue, 3 Feb 2026 10:29:56 +0000 Message-Id: <20260203103000.20206-9-david.laight.linux@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260203103000.20206-1-david.laight.linux@gmail.com> References: <20260203103000.20206-1-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: quoted-printable Content-Type: text/plain; charset="utf-8" From: David Laight Move %s inside the numeric block to optimise away one va_arg() call. Add support for %i, an alias for %d. Add support for %X, as an alias for %x (works but lower case A..F). Use the length returned by u64toa_r() to avoid strlen() for everything except %s and %m. Signed-off-by: David Laight --- tools/include/nolibc/stdio.h | 44 +++++++++++++++++++++++++----------- 1 file changed, 31 insertions(+), 13 deletions(-) diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h index e4792625c1ec..d8b6184ff0f3 100644 --- a/tools/include/nolibc/stdio.h +++ b/tools/include/nolibc/stdio.h @@ -241,7 +241,7 @@ char *fgets(char *s, int size, FILE *stream) =20 =20 /* simple printf(). It supports the following formats: - * - %[-+ ][width][{l,t,z,ll,L,j,q}]{d,u,c,x,p,s,m} + * - %[-+ ][width][{l,t,z,ll,L,j,q}]{d,i,u,c,x,X,p,s,m} * - %% * - invalid formats are copied to the output buffer */ @@ -254,7 +254,7 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state,= const char *fmt, va_list char c; int len, written, width; unsigned int flags; - char tmpbuf[64]; + char tmpbuf[32 + 24]; const char *outstr; =20 written =3D 0; @@ -304,13 +304,21 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *stat= e, const char *fmt, va_list } } =20 - if (c =3D=3D 'c' || c =3D=3D 'd' || c =3D=3D 'u' || c =3D=3D 'x' || c = =3D=3D 'p') { + /* Conversion specifiers are lower case except 'X' treated as 'x' */ + if (!((c >=3D 'a' && c <=3D 'z') || (c =3D=3D 'X' && (c =3D 'x')))) + goto bad_conversion_specifier; + + /* Conversion specifiers */ + if (__PF_FLAG(c) & (__PF_FLAG('c') | __PF_FLAG('d') | __PF_FLAG('i') | = __PF_FLAG('u') | + __PF_FLAG('x') | __PF_FLAG('p') | __PF_FLAG('s'))) { unsigned long long v; long long signed_v; char *out =3D tmpbuf + 32; int sign =3D 0; =20 - if ((c =3D=3D 'p') || (flags & (__PF_FLAG('l') | __PF_FLAG('t') | __PF= _FLAG('z')))) { + /* Annoying 'p' =3D=3D=3D '0' so mask from flags */ + if ((__PF_FLAG(c) | (flags & ~__PF_FLAG('p'))) & + (__PF_FLAG('p') | __PF_FLAG('s') | __PF_FLAG('l') | __PF_FLAG('t')= | __PF_FLAG('z'))) { v =3D va_arg(args, unsigned long); signed_v =3D (long)v; } else if (flags & (__PF_FLAG('j') | __PF_FLAG('q'))) { @@ -327,7 +335,18 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state= , const char *fmt, va_list len =3D 1; outstr =3D tmpbuf; goto do_output; + case 's': + if (!v) { + outstr =3D "(null)"; + len =3D 6; + goto do_output; + } + outstr =3D (void *)v; +do_strnlen_output: + len =3D strnlen(outstr, INT_MAX); + goto do_output; case 'd': + case 'i': if (signed_v < 0) { sign =3D '-'; v =3D -(signed_v + 1); @@ -339,42 +358,41 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *stat= e, const char *fmt, va_list } __nolibc_fallthrough; case 'u': - u64toa_r(v, out); + len =3D u64toa_r(v, out); break; case 'p': sign =3D 'x' | '0' << 8; __nolibc_fallthrough; default: /* 'x' and 'p' above */ - u64toh_r(v, out); + len =3D u64toh_r(v, out); break; } for (; sign; sign >>=3D 8) { + len++; *--out =3D sign; } outstr =3D out; } - else if (c =3D=3D 's') { - outstr =3D va_arg(args, char *); - if (!outstr) - outstr=3D"(null)"; - } else if (c =3D=3D 'm') { #ifdef NOLIBC_IGNORE_ERRNO outstr =3D "unknown error"; + len =3D __builtin_strlen(outstr); #else outstr =3D strerror(errno); + goto do_strnlen_output; #endif /* NOLIBC_IGNORE_ERRNO */ } else { +bad_conversion_specifier: if (c !=3D '%') /* Invalid format, output the format string */ fmt =3D outstr + 1; /* %% is documented as a 'conversion specifier'. * Any flags, precision or length modifier are ignored. */ + outstr =3D fmt - 1; + len =3D 1; width =3D 0; - outstr =3D "%"; } - len =3D strlen(outstr); } =20 do_output: --=20 2.39.5