From: David Laight Date: Sun, 8 Mar 2026 11:37:38 +0000 (+0000) Subject: tools/nolibc/printf: Special case 0 and add support for %#x X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5eae5f1a01aff6f9773547265167d7a680c6fbc3;p=thirdparty%2Fkernel%2Flinux.git tools/nolibc/printf: Special case 0 and add support for %#x The output for %#x is almost the same as that for %p, both output in hexadecimal with a leading "0x". However for zero %#x should just output "0" (the same as decimal and ocal). For %p match glibc and output "(nil)" rather than "0x0" or "0". Add tests for "%#x", "% d", "%+d" and passing NULL to "%p". Signed-off-by: David Laight Acked-by: Willy Tarreau Link: https://patch.msgid.link/20260308113742.12649-14-david.laight.linux@gmail.com [Thomas: fix up testcases for musl libc] Signed-off-by: Thomas Weißschuh --- diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h index 65e113f135d45..db714b1ce2744 100644 --- a/tools/include/nolibc/stdio.h +++ b/tools/include/nolibc/stdio.h @@ -296,7 +296,7 @@ int fseek(FILE *stream, long offset, int whence) * - %% generates a single % * - %m outputs strerror(errno). * - %X outputs a..f the same as %x. - * - The modifiers [#-0] are currently ignored. + * - 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. @@ -410,8 +410,11 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list * so that 'X' can be allowed through. * 'X' gets treated and 'x' because _NOLIBC_PF_FLAG() returns the same * value for both. + * + * We need to check for "%p" or "%#x" later, merging here gives better code. + * But '#' collides with 'c' so shift right. */ - ch_flag = _NOLIBC_PF_FLAG(ch); + ch_flag = _NOLIBC_PF_FLAG(ch) | (flags & _NOLIBC_PF_FLAG('#')) >> 1; if (((ch >= 'a' && ch <= 'z') || ch == 'X') && _NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'c', 'd', 'i', 'u', 'x', 'p', 's')) { /* 'long' is needed for pointer/string conversions and ltz lengths. @@ -471,17 +474,30 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list */ out = outbuf + 2; - /* Convert the number to ascii in the required base. */ - if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'd', 'i', 'u')) { - /* Base 10 */ - len = u64toa_r(v, out); - } else { - /* Base 16 */ + if (v == 0) { + /* There are special rules for zero. */ if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'p')) { - /* "%p" needs "0x" prepending. */ - sign_prefix = '0' << 8 | 'x'; + /* "%p" match glibc, precision is ignored */ + outstr = "(nil)"; + len = 5; + goto do_output; + } + /* All other formats (including "%#x") just output "0". */ + out[0] = '0'; + len = 1; + } else { + /* Convert the number to ascii in the required base. */ + if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'd', 'i', 'u')) { + /* Base 10 */ + len = u64toa_r(v, out); + } else { + /* Base 16 */ + if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'p', '#' - 1)) { + /* "%p" and "%#x" need "0x" prepending. */ + sign_prefix = '0' << 8 | 'x'; + } + len = u64toh_r(v, out); } - len = u64toh_r(v, out); } /* Add the 0, 1 or 2 ("0x") sign/prefix characters at the front. */ diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 6fa2346c655a7..9644087267d13 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -1833,6 +1833,7 @@ static int run_printf(int min, int max) CASE_TEST(string); EXPECT_VFPRINTF(1, "foo", "%s", "foo"); break; CASE_TEST(number); EXPECT_VFPRINTF(1, "1234", "%d", 1234); break; CASE_TEST(negnumber); EXPECT_VFPRINTF(1, "-1234", "%d", -1234); break; + CASE_TEST(num_sign); EXPECT_VFPRINTF(1, "| 1|+2|+3|+4|5|", "|% d|%+d|% +d|%+ d|%#d|", 1, 2, 3, 4, 5); break; CASE_TEST(unsigned); EXPECT_VFPRINTF(1, "12345", "%u", 12345); break; CASE_TEST(signed_max); EXPECT_VFPRINTF(1, "2147483647", "%i", ~0u >> 1); break; CASE_TEST(signed_min); EXPECT_VFPRINTF(1, "-2147483648", "%i", (~0u >> 1) + 1); break; @@ -1840,7 +1841,9 @@ static int run_printf(int min, int max) CASE_TEST(char); EXPECT_VFPRINTF(1, "c", "%c", 'c'); break; CASE_TEST(hex_nolibc); EXPECT_VFPRINTF(is_nolibc, "|f|d|", "|%x|%X|", 0xf, 0xd); break; CASE_TEST(hex_libc); EXPECT_VFPRINTF(!is_nolibc, "|f|D|", "|%x|%X|", 0xf, 0xd); break; + CASE_TEST(hex_alt); EXPECT_VFPRINTF(1, "|0x1| 0x2| 0|", "|%#x|%#5x|%#5x|", 1, 2, 0); break; CASE_TEST(pointer); EXPECT_VFPRINTF(1, "0x1", "%p", (void *) 0x1); break; + CASE_TEST(pointer_NULL); EXPECT_VFPRINTF(is_nolibc || is_glibc, "(nil)", "%p", (void *)0); break; CASE_TEST(percent); EXPECT_VFPRINTF(1, "a%d42%69%", "a%%d%d%%%d%%", 42, 69); break; CASE_TEST(perc_qual); EXPECT_VFPRINTF(is_nolibc || is_glibc, "a%d2", "a%-14l%d%d", 2); break; CASE_TEST(invalid); EXPECT_VFPRINTF(is_nolibc || is_glibc, "a%12yx3%y42%P", "a%12yx%d%y%d%P", 3, 42); break;