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Wed, 14 Jun 2023 07:29:09 -0700 (PDT) To: libc-alpha@sourceware.org Cc: fweimer@redhat.com Subject: [PATCH] manual: Document deviation of realloc from C2x/N2464 Date: Wed, 14 Jun 2023 10:28:55 -0400 Message-Id: <20230614142855.1535558-1-siddhesh@sourceware.org> X-Mailer: git-send-email 2.40.1 MIME-Version: 1.0 X-Spam-Status: No, score=-1172.7 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_NONE, KAM_DMARC_STATUS, KAM_NUMSUBJECT, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_SOFTFAIL, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Siddhesh Poyarekar via Libc-alpha From: Siddhesh Poyarekar Reply-To: Siddhesh Poyarekar Errors-To: libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org Sender: "Libc-alpha" Explicitly note that the realloc behaviour chosen in glibc is deliberate and well defined and suggest that strictly compliant code should avoid passing zero to realloc. Signed-off-by: Siddhesh Poyarekar --- manual/memory.texi | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/manual/memory.texi b/manual/memory.texi index 5781a64f35..7697a10f72 100644 --- a/manual/memory.texi +++ b/manual/memory.texi @@ -832,6 +832,11 @@ space is available. The value of @code{realloc} is the new address of the block. If the block needs to be moved, @code{realloc} copies the old contents. +The ISO C2x standard regards a zero value for @var{newsize} as undefined +through N2464, so code that aims to be strictly compliant should avoid passing +zero as @var{newsize} to @code{realloc}. @Theglibc{} behavior however is well +defined below. + If you pass a null pointer for @var{ptr}, @code{realloc} behaves just like @samp{malloc (@var{newsize})}. Otherwise, if @var{newsize} is zero