[a8 dos] Exit via DOSVEC (#332)

llvm-mos · May 30, 2024 · 8ed2b87 · 8ed2b87
1 parent e4aa926
commit 8ed2b87
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Showing 2 changed files with 10 additions and 2 deletions.
diff --git a/mos-platform/atari8-dos/CMakeLists.txt b/mos-platform/atari8-dos/CMakeLists.txt
@@ -4,10 +4,10 @@ if(NOT CMAKE_CROSSCOMPILING)
   return()
 endif()
 
-add_platform_library(atari8-dos-crt0)
+add_platform_library(atari8-dos-crt0 _Exit.c)
 merge_libraries(atari8-dos-crt0
   common-copy-zp-data
   common-zero-bss
-  common-exit-return
+  common-exit-custom
 )
 target_link_libraries(atari8-dos-crt0 PRIVATE common-asminc)
diff --git a/mos-platform/atari8-dos/_Exit.c b/mos-platform/atari8-dos/_Exit.c
@@ -0,0 +1,8 @@
+// Atari DOS 2.5 (etc?) does not correctly detect if a chunk after the first
+// clobbers the DUP, so it may crash after a RTS to DOS. Even if a DUP clobber
+// is detected, the effect is the same as a JMP through DOSVEC, so may as well.
+_Noreturn void _Exit(int status) {
+  // JMP (DOSVEC)
+  asm volatile("jmp ($a)");
+  __builtin_unreachable();
+}