adding GCC optimze O0 to early_fixmap_init causes compiler error (BUILD_BUG failed)

[Chan Kim]

I found adding the same #pragma directives warp to #include <linux/cache.h>
makes the compiler error go away!

 

#pragma GCC push_options

#pragma GCC optimize ("O0")

#include <linux/cache.h>

#pragma GCC pop_option

 

Chan

 

From: Chan Kim <ckim at etri.re.kr> 
Sent: Sunday, January 23, 2022 8:23 PM
To: kernelnewbies at kernelnewbies.org
Subject: adding GCC optimze O0 to early_fixmap_init causes compiler error
(BUILD_BUG failed) 

 

Hello all,

In linux 5.4.21, when tell the compiler to use no optimzation for function
early_fixmap_init as below,

(I need to compile with O0 to follow what's happening here using gdb.)

#pragma GCC push_options

#pragma GCC optimze ("O0")

void __init early_fixmap_init(void) 

{

...

}

#pragma GCC pop_options

 

I get this compiler error below. (make ARCH=arm64
CROSS_COMPILE=aarch64-none-elf- Image -j24)

CALL    scripts/atomic/check-atomics.sh

  CALL    scripts/checksyscalls.sh

  CHK     include/generated/compile.h

  CC      arch/arm64/mm/mmu.o

  CC      drivers/irqchip/irq-gic-v3.o

In file included from ./include/linux/build_bug.h:5,

                 from ./arch/arm64/include/asm/sysreg.h:758,

                 from ./arch/arm64/include/asm/cputype.h:126,

                 from ./arch/arm64/include/asm/cache.h:8,

                 from ./include/linux/cache.h:6,

                 from arch/arm64/mm/mmu.c:9:

./arch/arm64/include/asm/pgalloc.h: In function '__pgd_populate.constprop':

./include/linux/compiler.h:350:38: error: call to '__compiletime_assert_88'
declared with attribute error: BUILD_BUG failed

  350 |  _compiletime_assert(condition, msg, __compiletime_assert_,
__LINE__)

      |                                      ^

./include/linux/compiler.h:331:4: note: in definition of macro
'__compiletime_assert'

  331 |    prefix ## suffix();    \

      |    ^~~~~~

./include/linux/compiler.h:350:2: note: in expansion of macro
'_compiletime_assert'

  350 |  _compiletime_assert(condition, msg, __compiletime_assert_,
__LINE__)

      |  ^~~~~~~~~~~~~~~~~~~

./include/linux/build_bug.h:39:37: note: in expansion of macro
'compiletime_assert'

   39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)

      |                                     ^~~~~~~~~~~~~~~~~~

./include/linux/build_bug.h:59:21: note: in expansion of macro
'BUILD_BUG_ON_MSG'

   59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")

      |                     ^~~~~~~~~~~~~~~~

./arch/arm64/include/asm/pgalloc.h:88:2: note: in expansion of macro
'BUILD_BUG'

   88 |  BUILD_BUG();

      |  ^~~~~~~~~

make[2]: *** [scripts/Makefile.build:265: arch/arm64/mm/mmu.o] Error 1

make[1]: *** [scripts/Makefile.build:509: arch/arm64/mm] Error 2

make: *** [Makefile:1652: arch/arm64] Error 2

make: *** Waiting for unfinished jobs....

  AR      drivers/irqchip/built-in.a

AR      drivers/built-in.

 

What does this mean and what should I do?

Thanks!

Chan Kim

 

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