Date: Sun, 28 Aug 2016 04:25:46 +0300 From: Andrey Chernov <ache@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r304928 - in head/lib/libc: amd64/sys i386/sys sys Message-ID: <80ad9e03-74bc-8c99-666f-787772bef2b9@freebsd.org> In-Reply-To: <20160828011501.GH83214@kib.kiev.ua> References: <201608272303.u7RN3N0D078505@repo.freebsd.org> <9bcf10db-de3f-33ce-e418-03ce3283ac90@freebsd.org> <20160828005637.GG83214@kib.kiev.ua> <59ac1812-7c77-b677-51c4-dcadc6b2be7f@freebsd.org> <20160828011501.GH83214@kib.kiev.ua>
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On 28.08.2016 4:15, Konstantin Belousov wrote: >> POSIX: "No function in this volume of POSIX.1-2008 shall set errno to zero." > I am quite curious where ptrace(2) is defined by POSIX. POSIX just repeats C99 statement for its own functions, supporting this rule too, but C99 rule is more general and related to any library functions. >> POSIX: "For each thread of a process, the value of errno shall not be >> affected by function calls or assignments to errno by other threads." > And ? What should the citation add new to the substance > of the code change ? This is for your comment "On both i386 and amd64, the errno symbol was directly referenced, which only works correctly in single-threaded process." >> C99 statement sounds stricter: >> "The value of errno is zero at program startup, but is never set to zero >> by any library function. 176)" >> And syscall is not different from library function from C99 point of view. > Point me to a single line in C99 which mentions ptrace(). > > Do you understand what did the commit changed, and what it did not ? > Setting errno to zero before the syscall was the existing behaviour > before the change, and I did not modified anything there. But previous > wrapper set errno to zero in main thread even if called from some other > thread, which was the bug fixed. If you may notice, I don't blame you and don't say that you introduce setting errno to 0. I just want to bring your attention to the problem while you are in that area and familiar with it.
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