printf %g float passing on ARM crash

[chuckb]

I am compiling with gcc for ARM target...raspberry Pi zero. When I attempt to pass a float, I get a crash. CPU start up code enables the VFP with:

    // Enable VFP ------------------------------------------------------------

    // r1 = Access Control Register
    MRC p15, #0, r1, c1, c0, #2
    // enable full access for p10,11
    ORR r1, r1, #(0xf << 20)
    // Access Control Register = r1
    MCR p15, #0, r1, c1, c0, #2
    MOV r1, #0
    // flush prefetch buffer because of FMXR below
    MCR p15, #0, r1, c7, c5, #4
    // and CP 10 & 11 were only just enabled
    // Enable VFP itself
    MOV r0,#0x40000000
    // FPEXC = r0
    FMXR FPEXC, r0

My compile statement is like the following:

arm-none-eabi-gcc  -O2 -DRPI0 -Wall -fno-builtin -nostartfiles -fno-exceptions -fno-unwind-tables -mfpu=vfp -mfloat-abi=hard -mcpu=arm1176jzf-s -I"/Users/chuck_benedict/Projects/testHaikuVM/." -I"../../HaikuVM/src"  -I"../../HaikuVM/src/utility" -c -o "HaikuVM/src/heap.o" "../../HaikuVM/src/heap.c"
Finished building: ../../HaikuVM/src/heap.c

My link statement is:

arm-none-eabi-g++ -Wl,-T,/Users/chuck_benedict/Projects/haikuVM/haikuVM/src/lib/ldscripts/rpi.x,-Map,Main.map -nostartfiles -mfpu=vfp -mfloat-abi=hard -mcpu=arm1176jzf-s -o"Main.elf" -lm  ./HaikuVM/src/platforms/pi/printf.o ./HaikuVM/src/platforms/pi/rpi-gpio.o ./HaikuVM/src/platforms/pi/rpi-systimer.o ./HaikuVM/src/platforms/pi/rpi-armtimer.o ./HaikuVM/src/platforms/pi/rpi-aux.o ./HaikuVM/src/platforms/pi/armc-stubs.o ./HaikuVM/src/platforms/pi/rpi-mailbox.o ./HaikuVM/src/platforms/pi/rpi-mailbox-interface.o ./HaikuVM/src/platforms/pi/rpi-interrupts.o  ./HaikuVM/src/platforms/platform_AVR.o ./HaikuVM/src/platforms/platform_TEENSYDUINO.o ./HaikuVM/src/platforms/platform_RCX.o ./HaikuVM/src/platforms/platform_RPI.o ./HaikuVM/src/platforms/platform_WIN.o ./HaikuVM/src/platforms/platform_UNIX.o  ./HaikuVM/src/gcVariants/incremental.o ./HaikuVM/src/gcVariants/conservative.o ./HaikuVM/src/gcVariants/no.o  ./HaikuVM/src/utility/haikuJNI.o ./HaikuVM/src/utility/haikuConfig.o ./HaikuVM/src/utility/nativeCFunctions.o  ./HaikuVM/src/new4avrgcc.o ./HaikuVM/src/JVM.o ./HaikuVM/src/heap.o ./HaikuVM/src/HaikuAppMain.o ./HaikuVM/src/haikuJavaNatives.o ./HaikuVM/src/haikuJ2C.o ./HaikuVM/src/halfprecision.o ./HaikuVM/src/romspace.o    -lc

Can you help me with the magic incantation required to get this to work?

[AshkanAnousheh]

hi @chuckb ,
change your Floating Point setting to "Software Implementation" could solve your problem for now.

@mpaland thanks for your great library, please fix the bug.

[ledvinap]

Is it possible to get context of crash?
gdb backtrace + other printed info could help ...

[AshkanAnousheh]

This image shows Cortex-M4 processor status after vsnprintf function executed.

Program walk-through functions:
vsnprintf_() -> _vsnprintf() -> signal handler called at 0xfffffff9 -> stuck at WWDG_IRQHandler()

This error may contain useful information:
Develop Log System needs property 'FPU' fixed. Fixing from 'com.atollic.truestudio.common_options.target.fpucore.DUMMY' to 'com.atollic.truestudio.common_options.target.fpucore.fpv4-sp-d16'.

[ledvinap]

This is a bit strange - Window Watchdog IRQ is raised, either in place unrelated to FPU or frame for _ftoa is missing.
Cay you try compiling with -O0 to disable optimizations?
Also stepping through _ftoa may help.
Or you can try returning from IRQ (breaking the infinite loop) - use instruction stepping, change PC to same 'BX LR' instruction and step through it (I hope this works on ARM A processor)