vms-599: DEC C exit()/__posix_exit() record the VMS completion status (oracle-grounded)

src/vmslink/mk_decc_shr.sh

@@ -430,8 +430,24 @@ if [ "$OVMX_DECC_ARCH" = alpha ]; then
             esac
         done
         VEC=$(printf '%s' ",$VEC," | sed 's/,decc\$_getcwd64=PROCEDURE,/,decc$_getcwd64\/ovmx_crtl_getcwd=PROCEDURE,/; s/,decc\$getcwd\/decc\$_getcwd64=PROCEDURE,/,decc$getcwd\/ovmx_crtl_getcwd=PROCEDURE,/; s/^,//; s/,$//')
+        # vms-599: DEC C exit() records the image's VMS completion status (SYS$EXIT in
+        # LIBVMS$SHR) after musl's atexit handlers and stdio flush. decc$exit is rebound
+        # in place; __posix_exit (exit() under _POSIX_EXIT) is a new universal at the tail.
+        for _ex in ovmx_crtl_exit ovmx_crtl_posix_exit; do
+            "$NM" --defined-only "$SYS_OBJ" 2>/dev/null | awk '{print $NF}' | grep -qxF "$_ex" \
+                || { echo "mk_decc_shr: FAIL crtl_process.c did not define $_ex" >&2; exit 2; }
+        done
+        case ",$VEC," in
+            *',decc$exit=PROCEDURE,'*) ;;
+            *) echo "mk_decc_shr: FAIL decc\$exit is not a PROCEDURE universal to rebind" >&2; exit 2;;
+        esac
+        VEC=$(printf '%s' ",$VEC," | sed 's/,decc\$exit=PROCEDURE,/,decc$exit\/ovmx_crtl_exit=PROCEDURE,/; s/^,//; s/,$//')
+        case ",$VEC,${PASS2_TAIL:-}," in
+            *',decc$__posix_exit'[=/]*) echo "mk_decc_shr: FAIL decc\$__posix_exit is already in the vector" >&2; exit 2;;
+        esac
+        PASS2_TAIL="${PASS2_TAIL:-},decc\$__posix_exit/ovmx_crtl_posix_exit=PROCEDURE"
         ALPHA_VENEER_OBJ="$ALPHA_VENEER_OBJ $SYS_OBJ"
-        echo "mk_decc_shr: DEC C system() wired (vms-65a): decc\$system -> ovmx_crtl_system (LIB\$SPAWN, --use $ALPHA_CRTL_VMS_USE)"
+        echo "mk_decc_shr: DEC C system() wired (vms-65a): decc\$system -> ovmx_crtl_system (LIB\$SPAWN, --use $ALPHA_CRTL_VMS_USE); exit/__posix_exit record \$STATUS (vms-599)"
     fi
 
     # Plain (non-decc$-decorated) names the decc$ filter above cannot catch,

src/vmsrms/crtl_process.c

@@ -23,6 +23,21 @@
  * image. The musl system() the archive also carries (a clone with CLONE_VFORK,
  * which the executive refuses) stays an internal symbol: decc$system is rebound
  * in place to ovmx_crtl_system by mk_decc_shr.sh.
+ *
+ * exit() and __posix_exit() (vms-599): the value an image hands exit() is its VMS
+ * completion status, which DCL reads as $STATUS. Measured on OpenVMS Alpha V8.4
+ * (tests/lab/captures/decc-exit-alpha-20261021, MACRO-32 calling the C RTL entry
+ * points): DECC$EXIT turns 0 into %X00000001 (SS$_NORMAL) and passes every other
+ * value through unchanged (1, 2, 3, %X1000002C). DECC$__POSIX_EXIT (what exit()
+ * is under _POSIX_EXIT) keeps the low eight bits, turns 0 into %X00000001, and any
+ * other n into a C-facility message: %X0035A001 + (n << 3), with 1 made an error
+ * whose message is inhibited, %X1035A00A (2 -> %X0035A011, 255 -> %X0035A7F9,
+ * 256 -> %X00000001). musl's exit() ran the atexit handlers and flushed stdio, then
+ * exit_group()ed a POSIX code, and nothing recorded the status: DCL saw exit(1),
+ * a success, as "exited with error status %X00000001". Both entry points record
+ * the status, then run musl's exit; the C RTL file layer's system-call hook
+ * (crtl_rms_fd.c) sees the final exit_group and ends the image with SYS$EXIT of
+ * that status, after the handlers and the flush, as the DEC C RTL does.
  */
 #include <errno.h>
 #include <stdlib.h>
@@ -97,3 +112,48 @@ char *ovmx_crtl_getcwd(char *buf, unsigned long size, int vms_flag)
     memcpy(buf, out, need);
     return buf;
 }
+
+/* ------------------------------------------------------- exit (vms-599) ---- */
+
+extern unsigned int sys$exit(unsigned int code);            /* LIBVMS$SHR */
+extern void (*__ovmx_crtl_exit_record)(void);               /* crtl_rms_fd.c */
+
+static unsigned int crtl_exit_cond;
+
+/* Called from the system-call hook at the image's final exit_group: end the
+ * image with SYS$EXIT of the recorded status (it runs the exit handlers, records
+ * the status with the executive and terminates). The cell is cleared first, so
+ * SYS$EXIT's own exit_group passes straight through the hook. */
+static void crtl_exit_record(void)
+{
+    __ovmx_crtl_exit_record = 0;
+    (void)sys$exit(crtl_exit_cond);
+}
+
+static void crtl_exit_with(unsigned int cond)
+{
+    crtl_exit_cond = cond;
+    __ovmx_crtl_exit_record = crtl_exit_record;
+    exit((cond & 1u) ? 0 : 1);                     /* musl: atexit, stdio flush */
+}
+
+/* DEC C exit(): 0 is SS$_NORMAL, any other value is the status itself. */
+void ovmx_crtl_exit(int status)
+{
+    crtl_exit_with(status == 0 ? 1u : (unsigned int)status);
+}
+
+/* DEC C __posix_exit() (exit() under _POSIX_EXIT): a POSIX code 0-255 as a
+ * C-facility condition value (see the measurement above). */
+void ovmx_crtl_posix_exit(int status)
+{
+    unsigned int n = (unsigned int)status & 255u;
+    unsigned int cond;
+    if (n == 0)
+        cond = 1u;
+    else if (n == 1)
+        cond = 0x1035A00Au;
+    else
+        cond = 0x0035A001u + (n << 3);
+    crtl_exit_with(cond);
+}

src/vmsrms/crtl_rms_fd.c

@@ -1489,10 +1489,17 @@ static long long rms_hook_body(long long n, long long a1, long long a2,
     }
 }
 
+/* Set by the DEC C exit()/__posix_exit() (crtl_process.c, vms-599) to the routine
+ * that ends the image with SYS$EXIT of the status it was given; called at the
+ * final exit_group, after musl ran the atexit handlers and flushed stdio. */
+void (*__ovmx_crtl_exit_record)(void);
+
 static long long rms_hook(long long n, long long a1, long long a2, long long a3,
                           long long a4, long long a5, long long a6, int *handled)
 {
     (void)a6;
+    if (n == SYS_exit_group && __ovmx_crtl_exit_record)
+        __ovmx_crtl_exit_record();              /* SYS$EXIT: does not return */
     if (in_rms)
         return 0;                               /* RMS's own system calls */
     in_rms = 1;

tests/integration/test_userspace_service_register.sh

@@ -892,6 +892,12 @@ grep -E '\.[sS]$' "$WORK/buildset" > "$WORK/prodasm" 2>/dev/null || : > "$WORK/p
 # and only compiles inside the extracted musl tree. Its real compile runs in
 # build-musl.sh and its behaviour is proven by the alpha vfork gate. Anchored +
 # file-level, like lite_malloc.c above.
+# tools/cross-alpha-vms/musl-arch/src/exit/alpha-dec-vms/exit.c and
+# .../src/stdio/alpha-dec-vms/__stdio_exit.c (vms-599) are the same kind again
+# (src/<dir>/$(ARCH)/ replaces the generic file): they include musl's INTERNAL
+# "libc.h"/"stdio_impl.h" and define only exit() / __stdio_exit(), no sys$ symbol.
+# Its real compile + the exit nm gate run in build-musl.sh; the alpha crtl-fd gate
+# proves the behaviour. Anchored + file-level.
 # src/vmsrms/crtl_rms_fd.c (vms-b90) is the C RTL file layer DECC$SHR's
 # RMS-backed pass links: it hooks the musl-arch syscall funnel and fills musl's
 # arch-internal struct kstat (musl-arch kstat.h), so it only compiles against
@@ -917,7 +923,7 @@ grep -E '\.[sS]$' "$WORK/buildset" > "$WORK/prodasm" 2>/dev/null || : > "$WORK/p
 # the alpha-dec-vms client headers (musl-arch bits/stat.h: st_ino[3], st_fab_*,
 # the __OVMX_DECC_STAT_FIELDS list); a host libc has neither. They define no
 # sys$ service; their real compiles are mk_decc_shr.sh and the crtl-fd gate.
-SYMSCAN_EXCLUDE_RE="^src/kernel/|^src/kernel-netbsd/|^src/kernel-core/|^src/vmsfs/ods2/ods2_block_kern\.c$|^tools/cross-alpha-vms/musl-arch/src/internal/vms_alpha_syscall\.c$|^tools/cross-alpha-vms/musl-arch/src/thread/alpha-dec-vms/__set_thread_area\.c$|^tools/cross-alpha-vms/include-surface/compile_vms_unwind\.c$|^tools/cross-alpha-vms/musl-arch/src/malloc/alpha-dec-vms/lite_malloc\.c$|^tools/cross-alpha-vms/musl-arch/src/process/alpha-dec-vms/_Fork\.c$|^src/vmsrms/crtl_rms_fd\.c$|^src/vmsrms/rms_vmsabi\.c$|^tools/cross-alpha-vms/include-surface/vms_abi_headers\.c$|^tools/cross-alpha-vms/joint-e2e/vmsabi_rms_test\.c$|^src/vmslink/ovmx_decc_stat\.c$|^tools/cross-alpha-vms/joint-e2e/crtl_fd_test\.c$|^src/libvms/syssvc/sys_vmsabi\.c$|^tools/cross-alpha-vms/include-surface/hostabi_bfd_shapes\.c$"
+SYMSCAN_EXCLUDE_RE="^src/kernel/|^src/kernel-netbsd/|^src/kernel-core/|^src/vmsfs/ods2/ods2_block_kern\.c$|^tools/cross-alpha-vms/musl-arch/src/internal/vms_alpha_syscall\.c$|^tools/cross-alpha-vms/musl-arch/src/thread/alpha-dec-vms/__set_thread_area\.c$|^tools/cross-alpha-vms/include-surface/compile_vms_unwind\.c$|^tools/cross-alpha-vms/musl-arch/src/malloc/alpha-dec-vms/lite_malloc\.c$|^tools/cross-alpha-vms/musl-arch/src/process/alpha-dec-vms/_Fork\.c$|^tools/cross-alpha-vms/musl-arch/src/exit/alpha-dec-vms/exit\.c$|^tools/cross-alpha-vms/musl-arch/src/stdio/alpha-dec-vms/__stdio_exit\.c$|^src/vmsrms/crtl_rms_fd\.c$|^src/vmsrms/rms_vmsabi\.c$|^tools/cross-alpha-vms/include-surface/vms_abi_headers\.c$|^tools/cross-alpha-vms/joint-e2e/vmsabi_rms_test\.c$|^src/vmslink/ovmx_decc_stat\.c$|^tools/cross-alpha-vms/joint-e2e/crtl_fd_test\.c$|^src/libvms/syssvc/sys_vmsabi\.c$|^tools/cross-alpha-vms/include-surface/hostabi_bfd_shapes\.c$"
 
 SYMCC=""
 for _c in cc gcc; do

tests/lab/captures/decc-exit-alpha-20261021/CONSOLE.txt

@@ -0,0 +1,87 @@
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:EXS0.OBJ SYS$SCRATCH:EXS0.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:EXS0.EXE SYS$SCRATCH:EXS0.OBJ
+$ RUN SYS$SCRATCH:EXS0.EXE
+$ WRITE SYS$OUTPUT "PROBE EXS0 STATUS=",F$STRING($STATUS)
+PROBE EXS0 STATUS=%X00000001
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:EXS1.OBJ SYS$SCRATCH:EXS1.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:EXS1.EXE SYS$SCRATCH:EXS1.OBJ
+$ RUN SYS$SCRATCH:EXS1.EXE
+$ WRITE SYS$OUTPUT "PROBE EXS1 STATUS=",F$STRING($STATUS)
+PROBE EXS1 STATUS=%X00000001
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:EXS2.OBJ SYS$SCRATCH:EXS2.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:EXS2.EXE SYS$SCRATCH:EXS2.OBJ
+$ RUN SYS$SCRATCH:EXS2.EXE
+%NONAME-E-NOMSG, Message number 00000002
+$ WRITE SYS$OUTPUT "PROBE EXS2 STATUS=",F$STRING($STATUS)
+PROBE EXS2 STATUS=%X00000002
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:EXS3.OBJ SYS$SCRATCH:EXS3.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:EXS3.EXE SYS$SCRATCH:EXS3.OBJ
+$ RUN SYS$SCRATCH:EXS3.EXE
+$ WRITE SYS$OUTPUT "PROBE EXS3 STATUS=",F$STRING($STATUS)
+PROBE EXS3 STATUS=%X00000003
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:EXS4.OBJ SYS$SCRATCH:EXS4.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:EXS4.EXE SYS$SCRATCH:EXS4.OBJ
+$ RUN SYS$SCRATCH:EXS4.EXE
+%NONAME-F-NOMSG, Message number 00000004
+$ WRITE SYS$OUTPUT "PROBE EXS4 STATUS=",F$STRING($STATUS)
+PROBE EXS4 STATUS=%X00000004
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:EXSBIG.OBJ SYS$SCRATCH:EXSBIG.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:EXSBIG.EXE SYS$SCRATCH:EXSBIG.OBJ
+$ RUN SYS$SCRATCH:EXSBIG.EXE
+$ WRITE SYS$OUTPUT "PROBE EXSBIG STATUS=",F$STRING($STATUS)
+PROBE EXSBIG STATUS=%X1000002C
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:PXS0.OBJ SYS$SCRATCH:PXS0.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:PXS0.EXE SYS$SCRATCH:PXS0.OBJ
+$ RUN SYS$SCRATCH:PXS0.EXE
+$ WRITE SYS$OUTPUT "PROBE PXS0 STATUS=",F$STRING($STATUS)
+PROBE PXS0 STATUS=%X00000001
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:PXS1.OBJ SYS$SCRATCH:PXS1.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:PXS1.EXE SYS$SCRATCH:PXS1.OBJ
+$ RUN SYS$SCRATCH:PXS1.EXE
+$ WRITE SYS$OUTPUT "PROBE PXS1 STATUS=",F$STRING($STATUS)
+PROBE PXS1 STATUS=%X1035A00A
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:PXS2.OBJ SYS$SCRATCH:PXS2.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:PXS2.EXE SYS$SCRATCH:PXS2.OBJ
+$ RUN SYS$SCRATCH:PXS2.EXE
+$ WRITE SYS$OUTPUT "PROBE PXS2 STATUS=",F$STRING($STATUS)
+PROBE PXS2 STATUS=%X0035A011
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:PXS3.OBJ SYS$SCRATCH:PXS3.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:PXS3.EXE SYS$SCRATCH:PXS3.OBJ
+$ RUN SYS$SCRATCH:PXS3.EXE
+$ WRITE SYS$OUTPUT "PROBE PXS3 STATUS=",F$STRING($STATUS)
+PROBE PXS3 STATUS=%X0035A019
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:PXS255.OBJ SYS$SCRATCH:PXS255.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:PXS255.EXE SYS$SCRATCH:PXS255.OBJ
+$ RUN SYS$SCRATCH:PXS255.EXE
+$ WRITE SYS$OUTPUT "PROBE PXS255 STATUS=",F$STRING($STATUS)
+PROBE PXS255 STATUS=%X0035A7F9
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ MACRO/NOLIST/OBJECT=SYS$SCRATCH:PXS256.OBJ SYS$SCRATCH:PXS256.MAR
+$ LINK/EXECUTABLE=SYS$SCRATCH:PXS256.EXE SYS$SCRATCH:PXS256.OBJ
+$ RUN SYS$SCRATCH:PXS256.EXE
+$ WRITE SYS$OUTPUT "PROBE PXS256 STATUS=",F$STRING($STATUS)
+PROBE PXS256 STATUS=%X00000001
+$ SHOW SYMBOL $STATUS
+  $STATUS == "%X00010001"
+$ 

tests/lab/captures/decc-exit-alpha-20261021/EXS0.MAR

@@ -0,0 +1,7 @@
+        .TITLE  EXS0  OVMX exit-status probe: DECC$EXIT(0)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  EXS0,^M<>
+        PUSHL   #0
+        CALLS   #1,G^DECC$EXIT
+        RET
+        .END    EXS0

tests/lab/captures/decc-exit-alpha-20261021/EXS1.MAR

@@ -0,0 +1,7 @@
+        .TITLE  EXS1  OVMX exit-status probe: DECC$EXIT(1)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  EXS1,^M<>
+        PUSHL   #1
+        CALLS   #1,G^DECC$EXIT
+        RET
+        .END    EXS1

tests/lab/captures/decc-exit-alpha-20261021/EXS2.MAR

@@ -0,0 +1,7 @@
+        .TITLE  EXS2  OVMX exit-status probe: DECC$EXIT(2)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  EXS2,^M<>
+        PUSHL   #2
+        CALLS   #1,G^DECC$EXIT
+        RET
+        .END    EXS2

tests/lab/captures/decc-exit-alpha-20261021/EXS3.MAR

@@ -0,0 +1,7 @@
+        .TITLE  EXS3  OVMX exit-status probe: DECC$EXIT(3)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  EXS3,^M<>
+        PUSHL   #3
+        CALLS   #1,G^DECC$EXIT
+        RET
+        .END    EXS3

tests/lab/captures/decc-exit-alpha-20261021/EXS4.MAR

@@ -0,0 +1,7 @@
+        .TITLE  EXS4  OVMX exit-status probe: DECC$EXIT(4)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  EXS4,^M<>
+        PUSHL   #4
+        CALLS   #1,G^DECC$EXIT
+        RET
+        .END    EXS4

tests/lab/captures/decc-exit-alpha-20261021/EXSBIG.MAR

@@ -0,0 +1,7 @@
+        .TITLE  EXSBIG  OVMX exit-status probe: DECC$EXIT(%X1000002C)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  EXSBIG,^M<>
+        PUSHL   #^X1000002C
+        CALLS   #1,G^DECC$EXIT
+        RET
+        .END    EXSBIG

tests/lab/captures/decc-exit-alpha-20261021/PXS0.MAR

@@ -0,0 +1,7 @@
+        .TITLE  PXS0  OVMX exit-status probe: DECC$__POSIX_EXIT(0)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  PXS0,^M<>
+        PUSHL   #0
+        CALLS   #1,G^DECC$__POSIX_EXIT
+        RET
+        .END    PXS0

tests/lab/captures/decc-exit-alpha-20261021/PXS1.MAR

@@ -0,0 +1,7 @@
+        .TITLE  PXS1  OVMX exit-status probe: DECC$__POSIX_EXIT(1)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  PXS1,^M<>
+        PUSHL   #1
+        CALLS   #1,G^DECC$__POSIX_EXIT
+        RET
+        .END    PXS1

tests/lab/captures/decc-exit-alpha-20261021/PXS2.MAR

@@ -0,0 +1,7 @@
+        .TITLE  PXS2  OVMX exit-status probe: DECC$__POSIX_EXIT(2)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  PXS2,^M<>
+        PUSHL   #2
+        CALLS   #1,G^DECC$__POSIX_EXIT
+        RET
+        .END    PXS2

tests/lab/captures/decc-exit-alpha-20261021/PXS255.MAR

@@ -0,0 +1,7 @@
+        .TITLE  PXS255  OVMX exit-status probe: DECC$__POSIX_EXIT(255)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  PXS255,^M<>
+        PUSHL   #255
+        CALLS   #1,G^DECC$__POSIX_EXIT
+        RET
+        .END    PXS255

tests/lab/captures/decc-exit-alpha-20261021/PXS256.MAR

@@ -0,0 +1,7 @@
+        .TITLE  PXS256  OVMX exit-status probe: DECC$__POSIX_EXIT(256)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  PXS256,^M<>
+        PUSHL   #256
+        CALLS   #1,G^DECC$__POSIX_EXIT
+        RET
+        .END    PXS256

tests/lab/captures/decc-exit-alpha-20261021/PXS3.MAR

@@ -0,0 +1,7 @@
+        .TITLE  PXS3  OVMX exit-status probe: DECC$__POSIX_EXIT(3)
+        .PSECT  CCODE,EXE,NOWRT,QUAD
+        .ENTRY  PXS3,^M<>
+        PUSHL   #3
+        CALLS   #1,G^DECC$__POSIX_EXIT
+        RET
+        .END    PXS3

tests/lab/captures/decc-exit-alpha-20261021/README.md

@@ -0,0 +1,37 @@
+# DEC C exit() and __posix_exit() completion status on OpenVMS Alpha V8.4 (2026-10-21)
+
+Evidence for rd vms-599. Captured on a disposable lab pod (`exitalpha-1`, node `ALPHA1`,
+OpenVMS Alpha V8.4 on AXPbox), driven over the console FIFO with `tools/lab-alpha/`.
+The pod and its lab directory were deleted afterwards.
+
+The node has `MACRO` and `LINK` but no C compiler. Each probe is our own MACRO-32
+program, which calls the C RTL entry point directly with one value:
+`PUSHL #n` / `CALLS #1,G^DECC$EXIT` (or `DECC$__POSIX_EXIT`). The program is then
+`MACRO`ed, `LINK`ed and `RUN`, and `F$STRING($STATUS)` is printed (`CONSOLE.txt`).
+
+| call | `$STATUS` |
+|---|---|
+| `DECC$EXIT(0)` | `%X00000001` |
+| `DECC$EXIT(1)` | `%X00000001` |
+| `DECC$EXIT(2)` | `%X00000002` (DCL: `%NONAME-E-NOMSG`) |
+| `DECC$EXIT(3)` | `%X00000003` |
+| `DECC$EXIT(4)` | `%X00000004` (DCL: `%NONAME-F-NOMSG`) |
+| `DECC$EXIT(%X1000002C)` | `%X1000002C` |
+| `DECC$__POSIX_EXIT(0)` | `%X00000001` |
+| `DECC$__POSIX_EXIT(1)` | `%X1035A00A` |
+| `DECC$__POSIX_EXIT(2)` | `%X0035A011` |
+| `DECC$__POSIX_EXIT(3)` | `%X0035A019` |
+| `DECC$__POSIX_EXIT(255)` | `%X0035A7F9` |
+| `DECC$__POSIX_EXIT(256)` | `%X00000001` |
+
+So `exit()` turns 0 into SS$_NORMAL and passes every other value through unchanged.
+`__posix_exit()` keeps the low eight bits. It turns 0 into `%X00000001` and turns any
+other n into `%X0035A001 + (n << 3)`, a C-facility message with success severity.
+The one exception is 1: it becomes an error with the message inhibited, `%X1035A00A`.
+
+`EXIT_FAILURE` is a header constant and cannot be observed without a compiler. The VSI
+C RTL Reference (exit) groups "a status value of 2 or EXIT_FAILURE" as the error-level
+value, which matches the `%X00000002` measured above.
+
+Clean-room: observation only. Nothing was disassembled, and no VSI/HPE source or header
+was read.