Date: Tue, 31 Aug 2021 19:06:30 GMT From: Dimitry Andric <dim@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: ef314cd4bae2 - stable/13 - Fix null pointer subtraction in mergesort() Message-ID: <202108311906.17VJ6Uqm073674@gitrepo.freebsd.org>
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The branch stable/13 has been updated by dim: URL: https://cgit.FreeBSD.org/src/commit/?id=ef314cd4bae273be01eb45bae3af63680e65465c commit ef314cd4bae273be01eb45bae3af63680e65465c Author: Dimitry Andric <dim@FreeBSD.org> AuthorDate: 2021-08-27 17:45:43 +0000 Commit: Dimitry Andric <dim@FreeBSD.org> CommitDate: 2021-08-31 19:05:43 +0000 Fix null pointer subtraction in mergesort() Clang 13 produces the following warning for this function: lib/libc/stdlib/merge.c:137:41: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction] if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) ^ ~~~~~~~~~ This is meant to check whether the size and base parameters are aligned to the size of an int, so use our __is_aligned() macro instead. Also remove the comment that indicated this "stupid subtraction" was done to pacify some ancient and unknown Cray compiler, and which has been there since the BSD 4.4 Lite Lib Sources were imported. (cherry picked from commit 4e5d32a445f90d37966cd6de571978551654e3f3) --- lib/libc/stdlib/merge.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/lib/libc/stdlib/merge.c b/lib/libc/stdlib/merge.c index 853d6ae93fcb..7d8484ed10b9 100644 --- a/lib/libc/stdlib/merge.c +++ b/lib/libc/stdlib/merge.c @@ -129,12 +129,8 @@ mergesort(void *base, size_t nmemb, size_t size, cmp_t cmp) if (nmemb == 0) return (0); - /* - * XXX - * Stupid subtraction for the Cray. - */ iflag = 0; - if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) + if (__is_aligned(size, ISIZE) && __is_aligned(base, ISIZE)) iflag = 1; if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
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