linux-kernel - [PATCH] irqchip/stm32-exti: Fix warning on initialized field overwritten

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Date:   Thu, 1 Jun 2023 17:56:14 +0200
From:   Antonio Borneo <antonio.borneo@...s.st.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <llvm@...ts.linux.dev>
CC:     Antonio Borneo <antonio.borneo@...s.st.com>
Subject: [PATCH] irqchip/stm32-exti: Fix warning on initialized field overwritten

While compiling with W=1, both gcc and clang complain about a
tricky way to initialize an array by filling it with a non-zero
value and then overrride some of the array elements.
In this case the override is intentional, so just disable the
specific warning for only this part of the code.

Note: the flag "-Woverride-init" is recognized by both compilers,
but the warning msg from clang reports "-Winitializer-overrides".
The doc of clang clarifies that the two flags are synonyms, so use
here only the flag name common on both compilers.

Signed-off-by: Antonio Borneo <antonio.borneo@...s.st.com>
Fixes: c297493336b7 ("irqchip/stm32-exti: Simplify irq description table")
---
 drivers/irqchip/irq-stm32-exti.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/irqchip/irq-stm32-exti.c b/drivers/irqchip/irq-stm32-exti.c
index 6a3f7498ea8e..8bbb2b114636 100644
--- a/drivers/irqchip/irq-stm32-exti.c
+++ b/drivers/irqchip/irq-stm32-exti.c
@@ -173,6 +173,16 @@ static struct irq_chip stm32_exti_h_chip_direct;
 #define EXTI_INVALID_IRQ       U8_MAX
 #define STM32MP1_DESC_IRQ_SIZE (ARRAY_SIZE(stm32mp1_exti_banks) * IRQS_PER_BANK)
 
+/*
+ * Use some intentionally tricky logic here to initialize the whole array to
+ * EXTI_INVALID_IRQ, but then override certain fields, requiring us to indicate
+ * that we "know" that there are overrides in this structure, and we'll need to
+ * disable that warning from W=1 builds.
+ */
+__diag_push();
+__diag_ignore_all("-Woverride-init",
+		  "logic to initialize all and then override some is OK");
+
 static const u8 stm32mp1_desc_irq[] = {
 	/* default value */
 	[0 ... (STM32MP1_DESC_IRQ_SIZE - 1)] = EXTI_INVALID_IRQ,
@@ -266,6 +276,8 @@ static const u8 stm32mp13_desc_irq[] = {
 	[70] = 98,
 };
 
+__diag_pop();
+
 static const struct stm32_exti_drv_data stm32mp1_drv_data = {
 	.exti_banks = stm32mp1_exti_banks,
 	.bank_nr = ARRAY_SIZE(stm32mp1_exti_banks),

base-commit: 7877cb91f1081754a1487c144d85dc0d2e2e7fc4
-- 
2.40.1