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arm-none-eabi-ld: function call replaced with nop when linking against a
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From: |
Mykle James Hansen |
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Subject: |
arm-none-eabi-ld: function call replaced with nop when linking against archives, but not against objects -- bug? |
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Date: |
Tue, 18 Jun 2024 19:10:42 -0700 |
Hello. I think I might have hit a bug in arm-none-eabi-ld , the linker for the
ARM cross-compiler.
Below is a very long description. I also wrote this up in a github issue, which
may be easier
to read because it’s a bit better formatted.
That issue is here: https://github.com/technyon/Arduino-CMake-Toolchain/issues/7
Below is the same thing in plain text. In case it’s unclear, I found this
while comparing two build systems, “arduino-cli” and “cmake”, on the same
codebase.
The cmake version, which compiles .o files to .a file before linking the .elf,
is where I’m seeing the problem.
Maybe I’m just dumb and this isn’t a linker bug at all. I’d be happy to know
that.
——
I'm using an M1 Mac to compile an Arduino sketch for the RP2040 MCU. I'm using
these GCC-ARM versions, provided by the Homebrew project:
» arm-none-eabi-gcc --version
arm-none-eabi-gcc (Arm GNU Toolchain 13.2.rel1 (Build arm-13.7)) 13.2.1 20231009
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
» arm-none-eabi-ld -v
GNU ld (Arm GNU Toolchain 13.2.rel1 (Build arm-13.7)) 2.41.0.20231009
(I first hit this problem with version 12 arm-gcc provided by the RP2040
Arduino core,
then tried upgrading to version 13 but saw the same behavior.)
Below is an example sketch that shows the problem. It's just the basic Blink
example, plus opening a USB serial connection and writing a message. I'm using
the Adafruit-TinyUSB library option of the core (as opposed to the picousb
option) so USE_TINYUSB is defined.
#ifdef USE_TINYUSB
#include <Adafruit_TinyUSB.h>
#endif
// the setup function runs once when you press reset or power the board
void setup() {
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED_BUILTIN, OUTPUT);
// initialize USB Serial
Serial.begin(115200);
}
// the loop function runs over and over again forever
void loop() {
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on (HIGH is the voltage
level)
delay(1000); // wait for a second
digitalWrite(LED_BUILTIN, LOW); // turn the LED off by making the voltage
LOW
delay(1000); // wait for a second
Serial.println("boop");
}
The code compiles and runs correctly with arduino-cli.
With the build-system generated by Arduino-CMake-Toolchain, the code compiles
and runs, the blinking happens correctly, but the serial output does not.
Examining the build artifacts, it looks like the .elf output of the
Arduino-CMake build is missing some symbols (TinyUSB_Device_Init for one) that
initialize the Adafruit-TinyUSB library.
Here's the arduino-cli compiled .elf:
» arm-none-eabi-readelf -s abuild/Blink.ino.elf | grep TinyUSB
69: 00000000 0 FILE LOCAL DEFAULT ABS Adafruit_TinyUSB[...]
152: 00000000 0 FILE LOCAL DEFAULT ABS Adafruit_TinyUSB[...]
1495: 10003af1 20 FUNC GLOBAL DEFAULT 4 _Z21TinyUSB_Port[...]
1539: 10003b11 40 FUNC WEAK DEFAULT 4 TinyUSB_Device_Task
1656: 10003215 20 FUNC WEAK DEFAULT 4 TinyUSB_Device_Init
1670: 10003aad 68 FUNC GLOBAL DEFAULT 4 _Z23TinyUSB_Port[...]
1733: 10003229 32 FUNC WEAK DEFAULT 4 TinyUSB_Device_F[...]
1802: 10003b05 10 FUNC GLOBAL DEFAULT 4 _Z28TinyUSB_Port[...]
1891: 200013f8 404 OBJECT GLOBAL DEFAULT 11 TinyUSBDevice
And here's the cmake-compiled .elf:
» arm-none-eabi-readelf -s cbuild/Blink.elf | grep TinyUSB
233: 00000000 0 FILE LOCAL DEFAULT ABS Adafruit_TinyUSB[...]
1416: 10004111 20 FUNC GLOBAL DEFAULT 4 _Z21TinyUSB_Port[...]
1459: 10004131 40 FUNC WEAK DEFAULT 4 TinyUSB_Device_Task
1708: 10004125 10 FUNC GLOBAL DEFAULT 4 _Z28TinyUSB_Port[...]
1795: 20001328 404 OBJECT GLOBAL DEFAULT 11 TinyUSBDevice
... and in fact, in the cmake-compiled version of the core main() routine, ld
has actually replaced an unresolved link to <TinyUSB_Device_Init> with a nop
instead of reporting any kind of link failure. Should ld ever do such a thing?
TinyUSB_Device_Init is called from main.cpp in the Philhower RP2040 Arduino
core. This is the relevant code section with some undefined #ifdefs removed:
#ifdef USE_TINYUSB
TinyUSB_Device_Init(0);
#endif
Here's the relevant section from the (working) arduino-cli version, obtained
with arm-none-eabi-objdump -D -S abuild/Blink.ino.elf > Blink.ino.asm:
#ifdef USE_TINYUSB
TinyUSB_Device_Init(0);
10007bd8: 2000 movs r0, #0
10007bda: f7fb fb1b bl 10003214 <TinyUSB_Device_Init>
#endif
and the compiled code of <TinyUSB_Device_Init> is also present in that .elf
file:
10003214 <TinyUSB_Device_Init>:
//--------------------------------------------------------------------+
// Device
//--------------------------------------------------------------------+
#if CFG_TUD_ENABLED
void TinyUSB_Device_Init(uint8_t rhport) {
10003214: b510 push {r4, lr}
// Init USB Device controller and stack
TinyUSBDevice.begin(rhport);
10003216: 4b03 ldr r3, [pc, #12] @ (10003224 <TinyUSB_Device_Init+0x10>)
void TinyUSB_Device_Init(uint8_t rhport) {
10003218: 0001 movs r1, r0
TinyUSBDevice.begin(rhport);
1000321a: 0018 movs r0, r3
1000321c: f000 fa6c bl 100036f8 <_ZN20Adafruit_USBD_Device5beginEh>
}
10003220: bd10 pop {r4, pc}
10003222: 46c0 nop @ (mov r8, r8)
10003224: 200013f8 strdcs r1, [r0], -r8
10003228 <TinyUSB_Device_FlushCDC>:
tud_task();
}
#endif
That's all as you'd expect. But in the CMake-compiled version, obtained with
arm-none-eabi-objdump -D -S cbuild/Blink.elf > Blink.asm, the same section is
compiled like this:
#ifdef USE_TINYUSB
TinyUSB_Device_Init(0);
100034b0: 2000 movs r0, #0
100034b2: e000 b.n 100034b6 <main+0x9a>
100034b4: bf00 nop
#endif
... which means the call is just silently skipped. And the compiled code of
<TinyUSB_Device_Init> is not present at all.
In both builds USE_TINYUSB was defined for every compile step. (I tried
removing the #ifdef clause to force inclusion, with the same result.)
In both builds, main.cpp compiles correctly but unlinked. arduino-cli leaves it
in make.cpp.o, while the cmake build places it in the library
lib_arduino_lib_core.a, but the compiled code is the same:
TinyUSB_Device_Init(0);
72: 2000 movs r0, #0
74: f7ff fffe bl 0 <TinyUSB_Device_Init>
In both builds, TinyUSB_Device_Init() compiles correctly but unlinked. cmake
puts in in a library, lib_arduino_lib_Adafruit_TinyUSB.a, arduino-cli has it in
Adafruit_TinyUSB_API.cpp.o, but the code is identical:
Disassembly of section .text.TinyUSB_Device_Init:
00000000 <TinyUSB_Device_Init>:
//--------------------------------------------------------------------+
// Device
//--------------------------------------------------------------------+
#if CFG_TUD_ENABLED
void TinyUSB_Device_Init(uint8_t rhport) {
0: b510 push {r4, lr}
// Init USB Device controller and stack
TinyUSBDevice.begin(rhport);
2: 4b03 ldr r3, [pc, #12] ; (10 <TinyUSB_Device_Init+0x10>)
void TinyUSB_Device_Init(uint8_t rhport) {
4: 0001 movs r1, r0
TinyUSBDevice.begin(rhport);
6: 0018 movs r0, r3
8: f7ff fffe bl 0 <_ZN20Adafruit_USBD_Device5beginEh>
}
c: bd10 pop {r4, pc}
e: 46c0 nop ; (mov r8, r8)
10: 00000000 andeq r0, r0, r0
... and the other symbols all match as well. The code is all there, it's
compiled, it's just not linked correctly.
Obviously both toolchains are eventually just calling arm-none-eabi-g++ and the
other ARM-gcc tools. They appear to be calling them with all the same flags.
This is the final link command with arduino-cli (super-long, gack, sorry) that
produces a good .elf:
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/tools/pqt-gcc/2.2.0-d04e724/bin/arm-none-eabi-g++
-L/Volumes/External/mykle/Documents/Arduino/Blink/abuild -Werror=return-type
-Wno-psabi -DUSE_TINYUSB
-I/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/libraries/Adafruit_TinyUSB_Arduino/src/arduino
-DCFG_TUSB_MCU=OPT_MCU_RP2040 -DUSBD_PID=0x812d -DUSBD_VID=0x239a
-DUSBD_MAX_POWER_MA=250 "-DUSB_MANUFACTURER=\"Adafruit\""
"-DUSB_PRODUCT=\"Feather RP2040 RFM\""
-DPICO_CYW43_ARCH_THREADSAFE_BACKGROUND=1 -DCYW43_LWIP=1 -DLWIP_IPV6=0
-DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1
"-DARDUINO_VARIANT=\"adafruit_feather_rfm\"" -DTARGET_RP2040
-DPICO_FLASH_SIZE_BYTES=8388608 -march=armv6-m -mcpu=cortex-m0plus -mthumb
-ffunction-sections -fdata-sections -fno-exceptions -DARM_MATH_CM0_FAMILY
-DARM_MATH_CM0_PLUS -Os -u _printf_float -u _scanf_float
@/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/platform_wrap.txt
-Wl,--cref -Wl,--check-sections -Wl,--gc-sections
-Wl,--unresolved-symbols=report-all -Wl,--warn-common
-Wl,--script=/Volumes/External/mykle/Documents/Arduino/Blink/abuild/memmap_default.ld
-Wl,-Map,/Volumes/External/mykle/Documents/Arduino/Blink/abuild/Blink.ino.map
-o /Volumes/External/mykle/Documents/Arduino/Blink/abuild/Blink.ino.elf
-Wl,--no-warn-rwx-segments -Wl,--start-group
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/sketch/Blink.ino.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/Adafruit_TinyUSB_API.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/Adafruit_USBD_CDC.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/Adafruit_USBD_Device.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/Adafruit_USBD_Interface.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/Adafruit_USBH_Host.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/cdc/Adafruit_USBH_CDC.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/hid/Adafruit_USBD_HID.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/midi/Adafruit_USBD_MIDI.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/msc/Adafruit_USBD_MSC.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/msc/Adafruit_USBH_MSC.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/ports/esp32/Adafruit_TinyUSB_esp32.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/ports/nrf/Adafruit_TinyUSB_nrf.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/ports/rp2040/Adafruit_TinyUSB_rp2040.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/ports/samd/Adafruit_TinyUSB_samd.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/video/Adafruit_USBD_Video.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/arduino/webusb/Adafruit_USBD_WebUSB.cpp.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/audio/audio_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/bth/bth_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/cdc/cdc_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/cdc/cdc_host.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/dfu/dfu_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/dfu/dfu_rt_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/hid/hid_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/hid/hid_host.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/midi/midi_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/msc/msc_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/msc/msc_host.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/net/ecm_rndis_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/net/ncm_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/usbtmc/usbtmc_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/vendor/vendor_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/class/video/video_device.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/common/tusb_fifo.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/device/usbd.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/device/usbd_control.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/host/hub.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/host/usbh.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/analog/max3421/hcd_max3421.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/microchip/samd/dcd_samd.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/nordic/nrf5x/dcd_nrf5x.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/raspberrypi/pio_usb/dcd_pio_usb.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/raspberrypi/pio_usb/hcd_pio_usb.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/raspberrypi/rp2040/dcd_rp2040.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/raspberrypi/rp2040/hcd_rp2040.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/raspberrypi/rp2040/rp2040_usb.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/portable/synopsys/dwc2/dcd_dwc2.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/Adafruit_TinyUSB_Arduino/tusb.c.o
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/libraries/SPI/SPI.a
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/core/core.a
/Volumes/External/mykle/Documents/Arduino/Blink/abuild/boot2.o
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/ota.o
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/libpico.a
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/libpicow-noipv6-nobtc-noble.a
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/libbearssl.a
-lm -lc -lstdc++ -lc -Wl,--end-group
And here is the final link step with cmake (shorter but still horribly long)
that produces a bad .elf:
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/tools/pqt-gcc/2.2.0-d04e724/bin/arm-none-eabi-g++
-L/Volumes/External/mykle/Documents/Arduino/Blink/cbuild -Werror=return-type
-Wno-psabi -DUSE_TINYUSB
-I/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/libraries/Adafruit_TinyUSB_Arduino/src/arduino
-DCFG_TUSB_MCU=OPT_MCU_RP2040 -DUSBD_PID=0x812d -DUSBD_VID=0x239a
-DUSBD_MAX_POWER_MA=250 "-DUSB_MANUFACTURER=\"Adafruit\""
"-DUSB_PRODUCT=\"Feather RP2040 RFM\""
-DPICO_CYW43_ARCH_THREADSAFE_BACKGROUND=1 -DCYW43_LWIP=1 -DLWIP_IPV6=0
-DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1
"-DARDUINO_VARIANT=\"adafruit_feather_rfm\"" -DTARGET_RP2040
-DPICO_FLASH_SIZE_BYTES=8388608 -march=armv6-m -mcpu=cortex-m0plus -mthumb
-ffunction-sections -fdata-sections -fno-exceptions -DARM_MATH_CM0_FAMILY
-DARM_MATH_CM0_PLUS -Os -u _printf_float -u _scanf_float
@/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/platform_wrap.txt
-Wl,--cref -Wl,--check-sections -Wl,--gc-sections
-Wl,--unresolved-symbols=report-all -Wl,--warn-common
-Wl,--script=/Volumes/External/mykle/Documents/Arduino/Blink/cbuild/memmap_default.ld
-Wl,-Map,/Volumes/External/mykle/Documents/Arduino/Blink/cbuild/Blink.map -o
Blink.elf -Wl,--no-warn-rwx-segments -Wl,--start-group
CMakeFiles/Blink.dir/Blink.ino.cpp.o lib_arduino_lib_core.a
lib_arduino_lib_Adafruit_TinyUSB.a lib_arduino_lib_SPI.a
lib_arduino_lib_SdFat.a lib_arduino_lib_Adafruit_TinyUSB.a
lib_arduino_lib_SPI.a lib_arduino_lib_SdFat.a lib_arduino_lib_USB.a
lib_arduino_lib_FatFSUSB.a lib_arduino_lib_FatFS.a lib_arduino_lib_FS.a
lib_arduino_lib_FatFS.a lib_arduino_lib_FS.a lib_arduino_lib_ff.a
lib_arduino_lib_AudioBufferManager.a lib_arduino_lib_FreeRTOS.a
lib_arduino_lib_core.a
/Volumes/External/mykle/Documents/Arduino/Blink/cbuild/boot2.o
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/ota.o
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/libpico.a
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/libpicow-noipv6-nobtc-noble.a
/Volumes/External/mykle/Library/Arduino15/packages/rp2040/hardware/rp2040/3.9.2/lib/libbearssl.a
-lm -lc -lstdc++ -lc -Wl,--end-group
The only significant difference i can find in the build output between the two
processes is that the cmake process first bundles the objects into libraries,
and then does the final link against those libraries, while the arduino-cli
process compiles a zillion separate object files and then does the final link
against the entire list of them.
That shouldn't make a difference in the compiled code, right?
——
Thanks in advance for any help with this. I can gladly provide any/all of the
relevant files as needed,
or help in whatever other way is helpful.
-mykle-
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