From 98d62d70dc39859781c830aaf1b81a97a576d99c Mon Sep 17 00:00:00 2001 From: Jim Meyering Date: Thu, 24 Feb 2011 10:57:22 +0100 Subject: [PATCH] strstr: fix a bug whereby strstr would mistakenly return NULL * lib/str-two-way.h (two_way_short_needle): Correct off-by-one error in period calculation. (two_way_long_needle): Likewise. Reported by Ralf Wildenhues, with the short needle and haystack. * tests/test-strstr.c: Add Ralf's test case to trigger the bug. Add a more involved test to trigger the bug in two_way_long_needle. --- ChangeLog | 10 +++++++ lib/str-two-way.h | 4 +-- tests/test-strstr.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 91 insertions(+), 2 deletions(-) diff --git a/ChangeLog b/ChangeLog index 139b38f74..7795cce5e 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,13 @@ +2011-02-24 Jim Meyering + + strstr: fix a bug whereby strstr would mistakenly return NULL + * lib/str-two-way.h (two_way_short_needle): Correct off-by-one error + in period calculation. + (two_way_long_needle): Likewise. + Reported by Ralf Wildenhues, with the short needle and haystack. + * tests/test-strstr.c: Add Ralf's test case to trigger the bug. + Add a more involved test to trigger the bug in two_way_long_needle. + 2011-02-24 Stefano Lattarini (tiny change) gnulib-tool: remove use of bold display in help screen diff --git a/lib/str-two-way.h b/lib/str-two-way.h index dd8097667..317612c7b 100644 --- a/lib/str-two-way.h +++ b/lib/str-two-way.h @@ -284,7 +284,7 @@ two_way_short_needle (const unsigned char *haystack, size_t haystack_len, { /* The two halves of needle are distinct; no extra memory is required, and any mismatch results in a maximal shift. */ - period = MAX (suffix, needle_len - suffix) + 1; + period = MAX (suffix, needle_len - suffix); j = 0; while (AVAILABLE (haystack, haystack_len, j, needle_len)) { @@ -407,7 +407,7 @@ two_way_long_needle (const unsigned char *haystack, size_t haystack_len, /* The two halves of needle are distinct; no extra memory is required, and any mismatch results in a maximal shift. */ size_t shift; - period = MAX (suffix, needle_len - suffix) + 1; + period = MAX (suffix, needle_len - suffix); j = 0; while (AVAILABLE (haystack, haystack_len, j, needle_len)) { diff --git a/tests/test-strstr.c b/tests/test-strstr.c index f63cb33c9..718ead7f0 100644 --- a/tests/test-strstr.c +++ b/tests/test-strstr.c @@ -184,5 +184,84 @@ main (int argc, char *argv[]) /* Sublinear speed is only possible in memmem; strstr must examine every character of haystack to find its length. */ + + { + /* Ensure that with a barely periodic "short" needle, strstr's + search does not mistakenly skip just past the match point. + This use of strstr would mistakenly return NULL before + gnulib v0.0-4927. */ + const char *haystack = + "\n" + "with_build_libsubdir\n" + "with_local_prefix\n" + "with_gxx_include_dir\n" + "with_cpp_install_dir\n" + "enable_generated_files_in_srcdir\n" + "with_gnu_ld\n" + "with_ld\n" + "with_demangler_in_ld\n" + "with_gnu_as\n" + "with_as\n" + "enable_largefile\n" + "enable_werror_always\n" + "enable_checking\n" + "enable_coverage\n" + "enable_gather_detailed_mem_stats\n" + "enable_build_with_cxx\n" + "with_stabs\n" + "enable_multilib\n" + "enable___cxa_atexit\n" + "enable_decimal_float\n" + "enable_fixed_point\n" + "enable_threads\n" + "enable_tls\n" + "enable_objc_gc\n" + "with_dwarf2\n" + "enable_shared\n" + "with_build_sysroot\n" + "with_sysroot\n" + "with_specs\n" + "with_pkgversion\n" + "with_bugurl\n" + "enable_languages\n" + "with_multilib_list\n"; + const char *needle = "\n" + "with_gnu_ld\n"; + const char* p = strstr (haystack, needle); + ASSERT (p - haystack == 114); + } + + { + /* Like the above, but trigger the flaw in two_way_long_needle + by using a needle of length LONG_NEEDLE_THRESHOLD (32) or greater. + Rather than trying to find the right alignment manually, I've + arbitrarily chosen the following needle and template for the + haystack, and ensure that for each placement of the needle in + that haystack, strstr finds it. */ + const char *needle = "\nwith_gnu_ld-extend-to-len-32-b\n"; + const char *h = + "\n" + "with_build_libsubdir\n" + "with_local_prefix\n" + "with_gxx_include_dir\n" + "with_cpp_install_dir\n" + "with_e_\n" + "..............................\n" + "with_FGHIJKLMNOPQRSTUVWXYZ\n" + "with_567890123456789\n" "with_multilib_list\n"; + size_t h_len = strlen (h); + char *haystack = malloc (h_len + 1); + ASSERT (haystack); + size_t i; + for (i = 0; i < h_len - strlen (needle); i++) + { + memcpy (haystack, h, h_len + 1); + memcpy (haystack + i, needle, strlen (needle) + 1); + const char *p = strstr (haystack, needle); + ASSERT (p); + ASSERT (p - haystack == i); + } + } + return 0; } -- 2.11.0