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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [PATCH 1/2] Implement strlcpy and strlcat [BZ #178] Content-Language: en-US To: Alejandro Colomar , Florian Weimer , libc-alpha@sourceware.org References: <354b6c68-c692-25f0-089d-b7d7aad19b63@gmail.com> From: Siddhesh Poyarekar In-Reply-To: <354b6c68-c692-25f0-089d-b7d7aad19b63@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-3031.8 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 2023-04-06 17:29, Alejandro Colomar wrote: > Hi Siddhesh, > > On 4/6/23 16:22, Siddhesh Poyarekar wrote: > [...] > >>> +size_t >>> +__strlcpy (char *__restrict dest, const char *__restrict src, size_t size) >>> +{ >>> + size_t src_length = strlen (src); >>> + >>> + if (__glibc_unlikely (src_length >= size)) >>> + { >>> + if (size > 0) >>> + { >>> + /* Copy the leading portion of the string. The last >>> + character is subsequently overwritten with the NUL >>> + terminator, but the destination size is usually a >>> + multiple of a small power of two, so writing it twice >>> + should be more efficient than copying an odd number of >>> + bytes. */ >>> + memcpy (dest, src, size); >>> + dest[size - 1] = '\0'; >>> + } >>> + } >>> + else >>> + /* Copy the string and its terminating NUL character. */ >>> + memcpy (dest, src, src_length + 1); >> >> size == 0 is undefined anyway; we return without touching the dest >> because that's convenient for us. OK. > > Is it really convenient? What real code benefits of that behavior? > If we remove the conditional it's one less op. Hmm, and then maybe abort in __strlcpy_chk for size == 0. Thanks, Sid