[crt0] remove after-main handler

main should not return

docs/datasheet/software.adoc

@@ -510,7 +510,6 @@ The `crt0.S` start-up performs the following operations:
 ** All interrupt sources are disabled by clearing <<_mie>>.
 ** The return value of `main` is copied to the <<_mscratch>> CSR to allow inspection by the debugger.
 ** Call all _destructors_ (if there are any).
-** An optional <<_after_main_handler>> is called (if defined at all).
 ** The CPU enters sleep mode executing the `wfi` instruction in an endless loop.
 
 .Bootloader Start-Up Code
@@ -535,40 +534,6 @@ The early-trap handler should be replaced by a more capable / informative one as
 (for example by using the <<_neorv32_runtime_environment>>).
 
 
-:sectnums:
-===== After-Main Handler
-
-If the application's `main()` function actually returns, an _after main handler_ can be executed. This handler is a "normal" function
-as the C runtime is still available when executed. If this handler uses any kind of peripheral/IO modules make sure these are
-already initialized within the application. Otherwise you have to initialize them _inside_ the handler.
-
-.After-main handler - function prototype
-[source,c]
-----
-void __neorv32_crt0_after_main(int32_t return_code);
-----
-
-The function has exactly one argument (`return_code`) that provides the _return value_ of the application's main function.
-For instance, this variable contains `-1` if the main function returned with `return -1;`. The after-main handler itself does
-not provide a return value.
-
-A simple UART output can be used to inform the user when the application's main function returns
-(this example assumes that UART0 has been already properly configured in the actual application):
-
-.After-main handler - simple example
-[source,c]
-----
-void __neorv32_crt0_after_main(int32_t return_code) {
-
-  neorv32_uart0_printf("\n<RTE> main function returned with exit code %i. </RTE>\n", return_code); <1>
-}
-----
-<1> Use `<RTE>` here to make clear this is a message comes from the runtime environment.
-
-[NOTE]
-The after-main handler is executed _after_ executing all destructor functions (if there are any at all).
-
-
 <<<
 // ####################################################################################################################
 

sw/common/crt0.S

@@ -191,20 +191,6 @@ __crt0_call_destructors_loop_end:
 #endif
 
 
-// ************************************************************************************************
-// Call "after main" handler (if there is any) if main really returns
-// ************************************************************************************************
-#ifndef make_bootloader              // after_main handler not supported for bootloader
-__crt0_main_aftermath:
-  .weak    __neorv32_crt0_after_main
-  la   ra, __neorv32_crt0_after_main
-  beqz ra, __crt0_main_aftermath_end // check if an aftermath handler has been specified
-  jalr ra                            // execute handler with main's return code still in a0
-
-__crt0_main_aftermath_end:
-#endif
-
-
 // ************************************************************************************************
 // Go to endless sleep mode
 // ************************************************************************************************