build: downgrade the no optimization ztest error to warning

The current approach of failing the build on ztest with no optimization
broke coverage builds, and generally raised some concerns about being
too aggressive.

Downgrade the error to a warning and rework the option to inhibit the
warning, while also dropping it automatically for POSIX (that are not
really affected by stack size) and coverage run (that always runs with
no optimization).

Will reconsider this down the road if we still see issues filed for the
tests broken with no optimization and no further tuning.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>

CMakeLists.txt

@@ -705,11 +705,12 @@ endif()
 if(CONFIG_ZTEST)
   list(APPEND SYSCALL_INCLUDE_DIRS ${ZEPHYR_BASE}/subsys/testsuite/ztest/include)
 
-  if(CONFIG_NO_OPTIMIZATIONS AND NOT CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS)
-    message(FATAL_ERROR "Running tests with CONFIG_NO_OPTIMIZATIONS is not "
-    "supported and known to break many tests, please do not file issues about "
-    "it. If you really mean to do this also enable "
-    "CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS.")
+  if(CONFIG_NO_OPTIMIZATIONS AND CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS)
+    message(WARNING "Running tests with CONFIG_NO_OPTIMIZATIONS is generally "
+    "not supported and known to break in many cases due to stack overflow or "
+    "other problems. Please do not file issues about it unless the test is "
+    "specifically tuned to run in this configuration. To disable this warning "
+    "set CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS=n.")
   endif()
 
 endif()

boards/posix/nrf52_bsim/Kconfig.defconfig

@@ -51,7 +51,4 @@ config UART_CONSOLE
 
 endif # CONSOLE
 
-config ZTEST_ALLOW_NO_OPTIMIZATIONS
-	default y if ZTEST
-
 endif # BOARD_NRF52_BSIM

subsys/testsuite/ztest/Kconfig

@@ -103,13 +103,14 @@ config ZTEST_NO_YIELD
 	  yielding to the idle thread may put the board into a low power state
 	  where a debugger cannot connect to it.
 
-config ZTEST_ALLOW_NO_OPTIMIZATIONS
-	bool "Allow running tests with CONFIG_NO_OPTIMIZATIONS"
+config ZTEST_WARN_NO_OPTIMIZATIONS
+	bool "Warn when running tests with CONFIG_NO_OPTIMIZATIONS"
+	default y if !(ARCH_POSIX || COVERAGE)
 	depends on NO_OPTIMIZATIONS
 	help
-	  Do not error out when building a test without compiler optimization.
-	  This is normally not supported, please don't file issues when running
-	  tests that are not explicitly tuned to work in this configuration.
+	  Print a CMake warning when building ztests with no compiler
+	  optimizations. Please don't file issues when running tests that are
+	  not explicitly tuned to work in this configuration.
 
 if ZTEST_NEW_API
 

tests/arch/arm/arm_interrupt/testcase.yaml

@@ -13,7 +13,7 @@ tests:
     filter: not CONFIG_TRUSTED_EXECUTION_NONSECURE
     extra_configs:
       - CONFIG_NO_OPTIMIZATIONS=y
-      - CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS=y
+      - CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS=n
       - CONFIG_IDLE_STACK_SIZE=512
       - CONFIG_MAIN_STACK_SIZE=2048
   arch.interrupt.extra_exception_info:

tests/arch/arm/arm_thread_swap/testcase.yaml

@@ -11,7 +11,7 @@ tests:
     filter: not CONFIG_TRUSTED_EXECUTION_NONSECURE
     extra_configs:
       - CONFIG_NO_OPTIMIZATIONS=y
-      - CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS=y
+      - CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS=n
       - CONFIG_IDLE_STACK_SIZE=512
       - CONFIG_MAIN_STACK_SIZE=2048
     min_flash: 192
@@ -26,7 +26,7 @@ tests:
       - CONFIG_FPU=y
       - CONFIG_FPU_SHARING=y
       - CONFIG_NO_OPTIMIZATIONS=y
-      - CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS=y
+      - CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS=n
       - CONFIG_IDLE_STACK_SIZE=512
       - CONFIG_MAIN_STACK_SIZE=2048
     min_flash: 192

tests/subsys/logging/log_stack/testcase.yaml

@@ -16,7 +16,7 @@ tests:
     extra_configs:
       - CONFIG_LOG_MODE_DEFERRED=y
       - CONFIG_NO_OPTIMIZATIONS=y
-      - CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS=y
+      - CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS=n
       - CONFIG_IDLE_STACK_SIZE=2048
   logging.log_stack_immediate:
     extra_configs:
@@ -26,7 +26,7 @@ tests:
     extra_configs:
       - CONFIG_LOG_MODE_IMMEDIATE=y
       - CONFIG_NO_OPTIMIZATIONS=y
-      - CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS=y
+      - CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS=n
       - CONFIG_IDLE_STACK_SIZE=2048
   logging.log_stack_deferred_cpp:
     extra_configs:
@@ -37,7 +37,7 @@ tests:
     extra_configs:
       - CONFIG_LOG_MODE_DEFERRED=y
       - CONFIG_NO_OPTIMIZATIONS=y
-      - CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS=y
+      - CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS=n
       - CONFIG_CPP=y
   logging.log_stack_immediate_cpp:
     extra_configs:
@@ -48,5 +48,5 @@ tests:
     extra_configs:
       - CONFIG_LOG_MODE_IMMEDIATE=y
       - CONFIG_NO_OPTIMIZATIONS=y
-      - CONFIG_ZTEST_ALLOW_NO_OPTIMIZATIONS=y
+      - CONFIG_ZTEST_WARN_NO_OPTIMIZATIONS=n
       - CONFIG_CPP=y