From ef0a39547c1e4122a9e7d6c0256f05ed3a0512f6 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Thu, 7 Jun 2018 18:02:21 +0200
Subject: [PATCH] mescc: Support gcc-3.0: Implement atexit.

---
 include/stdlib.h     |  4 +++-
 include/unistd.h     |  3 ---
 lib/gcc.c            |  8 ++++++++
 lib/linux-mini-gcc.c | 14 ++++++++++++--
 lib/linux-mini-mes.c | 12 +++++++++++-
 5 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/include/stdlib.h b/include/stdlib.h
index 1c747e4b..46cbd286 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -40,8 +40,10 @@ void * alloca (unsigned size);
 void * alloca (size_t size);
 #endif
 int atoi (char const *s);
+int atexit (void (*function) (void));
 void * calloc (size_t nmemb, size_t size);
-void exit (int);
+void _exit (int status);
+void exit (int status);
 void free (void *ptr);
 char* getenv (char const* s);
 int setenv (char const* s, char const* v, int overwrite_p);
diff --git a/include/unistd.h b/include/unistd.h
index 391b19a4..26632a2b 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -90,9 +90,6 @@ typedef int pid_t;
 
 int access (char const *s, int mode);
 unsigned int alarm (unsigned int seconds);
-#define alarm(x) {eputs ("alarm x="); eputs (itoa (x)); eputs ("\n"); kill (getpid (), 14);}
-#define atexit(x) eputs ("atexit\n")
-
 int close (int fd);
 int execv (char const *file_name, char *const argv[]);
 int execve (char const *file, char *const argv[], char *const env[]);
diff --git a/lib/gcc.c b/lib/gcc.c
index 45fa72fd..e74d505e 100644
--- a/lib/gcc.c
+++ b/lib/gcc.c
@@ -80,3 +80,11 @@ unsetenv (char const *name)
       p++;
     }
 }
+
+// gcc-3.0
+int
+atexit (void (*function) (void))
+{
+  __call_at_exit = function;
+}
+
diff --git a/lib/linux-mini-gcc.c b/lib/linux-mini-gcc.c
index da05ccf4..3fe3829d 100644
--- a/lib/linux-mini-gcc.c
+++ b/lib/linux-mini-gcc.c
@@ -22,7 +22,7 @@
 #define SYS_write  "0x04"
 
 void
-exit (int code)
+_exit (int code)
 {
 #if !__TINYC__
   asm (
@@ -42,7 +42,17 @@ exit (int code)
        );
 #endif // __TINYC__
   // not reached
-  exit (0);
+  _exit (0);
+}
+
+void (*__call_at_exit) (void);
+
+void
+exit (int code)
+{
+  if (__call_at_exit)
+    (*__call_at_exit) ();
+  _exit (code);
 }
 
 ssize_t
diff --git a/lib/linux-mini-mes.c b/lib/linux-mini-mes.c
index 34955216..f2858a1f 100644
--- a/lib/linux-mini-mes.c
+++ b/lib/linux-mini-mes.c
@@ -19,13 +19,23 @@
  */
 
 void
-exit ()
+_exit ()
 {
   asm ("mov____$i32,%eax SYS_exit");
   asm ("mov____0x8(%ebp),%ebx !8");
   asm ("int____$0x80");
 }
 
+void (*__call_at_exit) (void);
+
+void
+exit (int code)
+{
+  if (__call_at_exit)
+    (*__call_at_exit) ();
+  _exit (code);
+}
+
 void
 write ()
 {