Double definition of WDT for SAMD51

[amasmiller]

When the Feather M4 bootloader is compiled and modifications are made to use the RESET_CONTROLLER->RCAUSE.bit.WDT field, the bootloader fails to compile to due another definition of WDT.

Example code modifications:

diff --git a/Makefile b/Makefile
index 435a75c..4cb5ad9 100755
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-BOARD=zero
+BOARD=feather_m4
 -include Makefile.user
 include boards/$(BOARD)/board.mk
 CC=arm-none-eabi-gcc
diff --git a/src/main.c b/src/main.c
index 095fa0a..51b5caf 100644
--- a/src/main.c
+++ b/src/main.c
@@ -293,6 +293,11 @@ int main(void) {
     /* Jump in application if condition is satisfied */
     check_start_application();

+    if (RESET_CONTROLLER->RCAUSE.bit.WDT)
+    {
+        // noop
+    }
+
     /* We have determined we should stay in the monitor. */
     /* System initialization */
     system_init();

Resulting compilation output:

$ make
Building feather_m4
echo "src/main.c"
src/main.c
arm-none-eabi-gcc -mthumb -mcpu=cortex-m4 -O2 -g -DSAMD51 -x c -c -pipe -nostdlib --param max-inline-insns-single=500 -fno-strict-aliasing -fdata-sections -ffunction-sections -D__SAMD51J19A__ -Werror -Wall -Wstrict-prototypes -Werror-implicit-function-declaration -Wpointer-arith -std=gnu99 -ffunction-sections -fdata-sections -Wchar-subscripts -Wcomment -Wformat=2 -Wimplicit-int -Wmain -Wparentheses -Wsequence-point -Wreturn-type -Wswitch -Wtrigraphs -Wunused -Wuninitialized -Wunknown-pragmas -Wfloat-equal -Wno-undef -Wbad-function-cast -Wwrite-strings -Waggregate-return -Wformat -Wmissing-format-attribute -Wno-deprecated-declarations -Wpacked -Wredundant-decls -Wnested-externs -Wlong-long -Wunreachable-code -Wcast-align -Wno-missing-braces -Wno-overflow -Wno-shadow -Wno-attributes -Wno-packed -Wno-pointer-sign  -I. -I./inc -I./inc/preprocessor -I./boards/feather_m4 -Ilib/cmsis/CMSIS/Include -Ilib/usb_msc -Ibuild/feather_m4 -Ilib/samd51/include/ src/main.c -o build/feather_m4/main.o
In file included from lib/samd51/include/sam.h:38,
                 from ./inc/uf2.h:7,
                 from src/main.c:81:
src/main.c: In function 'main':
lib/samd51/include/samd51j19a.h:1016:27: error: expected identifier before '(' token
 #define WDT               ((Wdt      *)0x40002000UL) /**< \brief (WDT) APB Base Address */
                           ^
src/main.c:296:38: note: in expansion of macro 'WDT'
     if (RESET_CONTROLLER->RCAUSE.bit.WDT)
                                      ^~~
make: *** [Makefile:181: build/feather_m4/main.o] Error 1

The conflict of WDT is caused by the definitions in lib/samd51/include/component/rstc.h and lib/samd51/include/samd51j19a.h.

Current workaround is to use an #undef of WDT prior to use of the bit, as seen below:

diff --git a/src/main.c b/src/main.c
index 095fa0a..ddafeb6 100644
--- a/src/main.c
+++ b/src/main.c
@@ -293,6 +293,12 @@ int main(void) {
     /* Jump in application if condition is satisfied */
     check_start_application();

+    #undef WDT
+    if (RESET_CONTROLLER->RCAUSE.bit.WDT)
+    {
+        // noop
+    }
+
     /* We have determined we should stay in the monitor. */
     /* System initialization */
     system_init();