[Bug c/66547] New: arm-none-eabi-gcc - stack misaligned when calling va_arg function

["matt at hpamotorsport dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66547

            Bug ID: 66547
           Summary: arm-none-eabi-gcc - stack misaligned when calling
                    va_arg function
           Product: gcc
           Version: 4.9.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: matt at hpamotorsport dot com
  Target Milestone: ---

Created attachment 35785
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35785&action=edit
File from project

I'm working on a project that uses ChibiOS
(https://github.com/ChibiOS/ChibiOS/tree/stable_2.6.x) where I have a function
that calls a va_arg function but the stack is not aligned after the calling
function allocates it's local resources. This causes 64-bit variables (long
long as well as double) to be incorrectly placed.

The assembly generated shows that the stack pointer is moved by 116 where it
should be moved by 120 to keep the alignment to 8-bytes.




arm-none-eabi-gcc -c -mcpu=cortex-m3 -Os -ggdb -fsingle-precision-constant
-mno-unaligned-access -mabi=aapcs -mtune=cortex-m3 -save-temps
-ffunction-sections -fdata-sections -fno-common  -Wall -Wextra
-Wstrict-prototypes -Wa,-alms=build/lst/performance.lst  -DCORTEX_USE_FPU=FALSE
-DBOARD_HALDEX_STM32_P105_A1=1 -DOSC_HAS_64BIT -DOSC_HAS_FLOAT
-DOSC_HAS_HEARTBEAT -DSLP_HAS_USB -D__BUILD_NUMBER=`cat build-number.txt`
-DTHUMB_PRESENT -mno-thumb-interwork -DTHUMB_NO_INTERWORKING -MD -MP -MF
.dep/performance.o.d -mthumb -DTHUMB -I.
-I../ChibiOS_2.6.7/os/ports/common/ARMCMx/CMSIS/include
-I../ChibiOS_2.6.7/os/ports/common/ARMCMx
-I../ChibiOS_2.6.7/os/ports/GCC/ARMCMx
-I../ChibiOS_2.6.7/os/ports/GCC/ARMCMx/STM32F1xx
-I../ChibiOS_2.6.7/os/kernel/include -I../ChibiOS_2.6.7/os/hal/include
-I../ChibiOS_2.6.7/os/hal/platforms/STM32F1xx
-I../ChibiOS_2.6.7/os/hal/platforms/STM32
-I../ChibiOS_2.6.7/os/hal/platforms/STM32/GPIOv1
-I../ChibiOS_2.6.7/os/hal/platforms/STM32/I2Cv1
-I../ChibiOS_2.6.7/os/hal/platforms/STM32/RTCv1
-I../ChibiOS_2.6.7/os/hal/platforms/STM32/SPIv1
-I../ChibiOS_2.6.7/os/hal/platforms/STM32/TIMv1
-I../ChibiOS_2.6.7/os/hal/platforms/STM32/USARTv1
-I../ChibiOS_2.6.7/os/hal/platforms/STM32/OTGv1 -I../HPA_Libraries/board
-I../ChibiOS_2.6.7/os/various -I../HPA_Libraries performance.c -o
build/obj/performance.o