diff --git a/code/os/win/win_entry.c b/code/os/win/win_entry.c
index 314fe29..5fa2b44 100644
--- a/code/os/win/win_entry.c
+++ b/code/os/win/win_entry.c
@@ -74,9 +74,11 @@ void mainCRTStartup() {
     srand(0);
     setlocale(LC_ALL, "C");
     _os_init_eh();
+
     int exit_code = main(arg_count, args);
 
-    ExitProcess(exit_code);
+    // we call exit because we want atexit routines run
+    exit(exit_code);
 }
 
 // This symbol is required to be present if we're using floating-point
diff --git a/code/os/win/win_io.c b/code/os/win/win_io.c
index 4059204..f7bb2af 100644
--- a/code/os/win/win_io.c
+++ b/code/os/win/win_io.c
@@ -10,5 +10,3 @@ void _os_file_write(void* ctx, size_t n, const char str[]) {
     DWORD written = 0;
     WriteFile((HANDLE) ctx, str, n, &written, NULL);
 }
-
-
diff --git a/code/stdlib/env.c b/code/stdlib/env.c
index 9e8b349..fb35a06 100644
--- a/code/stdlib/env.c
+++ b/code/stdlib/env.c
@@ -4,18 +4,38 @@
 
 #include <_os.h>
 
+typedef void (*ExitRoutine)(void);
+
+// The implementation shall support the registration
+// of at least 32 functions.
+static ExitRoutine _exit_routines[64];
+static int _exit_routine_count;
+
 _Noreturn void abort(void) {
     raise(SIGABRT);
     _os_exit(-69);
 }
 
-// TODO: at_exit handling
+int atexit(void (*func)(void)) {
+    if (_exit_routine_count >= COUNTOF(_exit_routines)) {
+        return 0;
+    }
+
+    _exit_routines[_exit_routine_count++] = func;
+    return 1;
+}
 
 _Noreturn void exit(int status) {
+    // doing them in reverse seems nicer
+    for (int i = _exit_routine_count; i--;) {
+        _exit_routines[i]();
+    }
+
     _os_exit(status);
 }
 
 _Noreturn void _Exit(int status) {
+    // doesn't run atexit routines
     _os_exit(status);
 }
 
diff --git a/inc/stdlib.h b/inc/stdlib.h
index 048665d..12f9761 100644
--- a/inc/stdlib.h
+++ b/inc/stdlib.h
@@ -3,13 +3,13 @@
 #include <stddef.h>
 
 #if !defined(__STDC_LIB_EXT1__)
-    #define __STDC_LIB_EXT1__
+#define __STDC_LIB_EXT1__
 #endif
 
 #ifdef __STDC_WANT_SECURE_LIB__
-    #if !defined(__STDC_WANT_LIB_EXT1__)
-        #define __STDC_WANT_LIB_EXT1__ 1
-    #endif
+#if !defined(__STDC_WANT_LIB_EXT1__)
+#define __STDC_WANT_LIB_EXT1__ 1
+#endif
 #endif
 
 #define EXIT_SUCCESS 0
@@ -36,6 +36,11 @@
 #define RAND_MAX 65536
 // #define MB_CUR_MAX 5
 
+// Microsoft extension, COUNTOF(x) counts array elements
+#ifndef COUNTOF
+#define COUNTOF(...) (sizeof(__VA_ARGS__) / sizeof((__VA_ARGS__)[0]))
+#endif
+
 double atof(const char *nptr);
 int atoi(const char *nptr);
 long int atol(const char *nptr);
@@ -59,7 +64,7 @@ void *malloc(size_t size);
 void *realloc(void *ptr, size_t size);
 
 _Noreturn void abort(void);
-// int atexit(void (*func)(void));
+int atexit(void (*func)(void));
 // int at_quick_exit(void (*func)(void));
 _Noreturn void exit(int status);
 _Noreturn void _Exit(int status);
diff --git a/test/test.c b/test/test.c
index d26020f..bdf2e73 100644
--- a/test/test.c
+++ b/test/test.c
@@ -16,7 +16,13 @@ int test() {
     return a;
 }
 
+void wack() {
+    printf("BYE!!!\n");
+}
+
 int main(int argc, char** argv) {
+    atexit(wack);
+
     test();
     char input[] = "A bird came down the walk";
     printf("Parsing the input string '%s'\n", input);
@@ -25,10 +31,10 @@ int main(int argc, char** argv) {
         printf("%s\n", token);
         token = strtok(NULL, " ");
     }
- 
+
     printf("Contents of the input string now: '");
     for(size_t n = 0; n < sizeof input; ++n)
         input[n] ? printf("%c", input[n]) : printf("\\0");
     printf("'");
     return 0;
-}
\ No newline at end of file
+}
diff --git a/test/test2.c b/test/test2.c
new file mode 100644
index 0000000..2ba72d0
--- /dev/null
+++ b/test/test2.c
@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
+
+int main(void) {
+    double v0 = strtod("0X1.BC70A3D70A3D7P+6", NULL);
+
+    // parsing with error handling
+    const char *p = "111.11 -2.22 Nan nan(2) inF 0X1.BC70A3D70A3D7P+6  1.18973e+4932zzz";
+
+    char *end;
+    for (double f = strtod(p, &end); p != end; f = strtod(p, &end)) {
+        // printf("'%.*s' -> ", (int)(end-p), p);
+        p = end;
+        if (errno == ERANGE){
+            // printf("range error, got ");
+            errno = 0;
+        }
+        // printf("%f\n", f);
+    }
+
+    // parsing without error handling
+    double v1 = strtod("  -0.0000000123junk", NULL);
+    double v2 = strtod("junk", NULL);
+}
diff --git a/test/test3.c b/test/test3.c
new file mode 100644
index 0000000..9c240ce
--- /dev/null
+++ b/test/test3.c
@@ -0,0 +1,9 @@
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
+
+int main(int argc, char** argv) {
+    for (int i = 0; i < argv; i++) {
+        printf("[%d] = %s\n", i, argv[i]);
+    }
+}