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Content-Language: en-US To: gcc-patches@gcc.gnu.org, richard.sandiford@arm.com References: <96e57488-2dba-f4f1-4215-9ee3f259bb3a@suse.cz> From: =?UTF-8?Q?Martin_Li=c5=a1ka?= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-12.2 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, NICE_REPLY_A, SPF_HELO_NONE, SPF_PASS, 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: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 May 2022 14:17:24 -0000 On 5/16/22 10:56, Richard Sandiford wrote: > Martin Liška writes: >> It's the warning I see every time I build GCC: >> >> In file included from /home/marxin/Programming/gcc/gcc/coretypes.h:478, >> from /home/marxin/Programming/gcc/gcc/expmed.cc:26: >> In function ‘poly_uint16 mode_to_bytes(machine_mode)’, >> inlined from ‘typename if_nonpoly::type GET_MODE_SIZE(const T&) [with T = scalar_int_mode]’ at /home/marxin/Programming/gcc/gcc/machmode.h:647:24, >> inlined from ‘rtx_def* emit_store_flag_1(rtx, rtx_code, rtx, rtx, machine_mode, int, int, machine_mode)’ at /home/marxin/Programming/gcc/gcc/expmed.cc:5728:56: >> /home/marxin/Programming/gcc/gcc/machmode.h:550:49: warning: ‘*(unsigned int*)((char*)&int_mode + offsetof(scalar_int_mode, scalar_int_mode::m_mode))’ may be used uninitialized [-Wmaybe-uninitialized] >> 550 | ? mode_size_inline (mode) : mode_size[mode]); >> | ^~~~ >> /home/marxin/Programming/gcc/gcc/expmed.cc: In function ‘rtx_def* emit_store_flag_1(rtx, rtx_code, rtx, rtx, machine_mode, int, int, machine_mode)’: >> /home/marxin/Programming/gcc/gcc/expmed.cc:5657:19: note: ‘*(unsigned int*)((char*)&int_mode + offsetof(scalar_int_mode, scalar_int_mode::m_mode))’ was declared here >> 5657 | scalar_int_mode int_mode; >> | ^~~~~~~~ >> >> Can we please mitigate it? >> >> gcc/ChangeLog: >> >> * expmed.cc (emit_store_flag_1): Mitigate -Wmaybe-uninitialized >> warning. > > Not a strong objection, but TBH I'd rather we didn't work around false > positives like this. Sure, but as you know, -Wmaybe-uninitialized has pretty high rate of false positivity :/ Martin > > Richard > >> --- >> gcc/expmed.cc | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/gcc/expmed.cc b/gcc/expmed.cc >> index 41738c1efe9..f23d63471ea 100644 >> --- a/gcc/expmed.cc >> +++ b/gcc/expmed.cc >> @@ -5654,7 +5654,7 @@ emit_store_flag_1 (rtx target, enum rtx_code code, rtx op0, rtx op1, >> >> /* If we are comparing a double-word integer with zero or -1, we can >> convert the comparison into one involving a single word. */ >> - scalar_int_mode int_mode; >> + scalar_int_mode int_mode = {}; >> if (is_int_mode (mode, &int_mode) >> && GET_MODE_BITSIZE (int_mode) == BITS_PER_WORD * 2 >> && (!MEM_P (op0) || ! MEM_VOLATILE_P (op0)))