Fix EXAMINE output for array register repeats

Adopt the fix from open-simh PR 502 for the bug described in upstream
issue 499, and add local test coverage.

When EXAMINE compresses repeated array register values, the old
single-element repeat case printed the skipped element with the next
different value. That made ranged output report an incorrect value for
the skipped array slot.

Remove that special case so every skipped repeated run is summarized as
`same as above`, whether it contains one element or several. Add a
focused SCP register unit test that reproduces the bad output before the
fix and validates the corrected summary output.

Author: pmetzger

src/core/scp.c

@@ -7876,18 +7876,10 @@ for (rptr = lowr; rptr <= highr; rptr++) {
             if ((idx > lows) && (val == last_val))
                 continue;
             if (idx > val_start+1) {
-                if (idx-1 == val_start+1) {
-                    reason = ex_reg (ofile, val, flag, rptr, idx-1);
-                    sim_switches = saved_switches;
-                    if (reason != SCPE_OK)
-                        return reason;
-                    }
-                else {
-                    if (val_start+1 != idx-1)
-                        fprintf (ofile, "%s[%d]-%s[%d]: same as above\n", rptr->name, val_start+1, rptr->name, idx-1);
-                    else
-                        fprintf (ofile, "%s[%d]: same as above\n", rptr->name, val_start+1);
-                    }
+                if (val_start+1 != idx-1)
+                    fprintf (ofile, "%s[%d]-%s[%d]: same as above\n", rptr->name, val_start+1, rptr->name, idx-1);
+                else
+                    fprintf (ofile, "%s[%d]: same as above\n", rptr->name, val_start+1);
                 }
             sim_last_val = last_val = val;
             val_start = idx;

src/core/scp.h

@@ -82,6 +82,8 @@
 
 t_stat reset_cmd (int32 flag, const char *ptr);
 t_stat exdep_cmd (int32 flag, const char *ptr);
+t_stat exdep_reg_loop (FILE *ofile, SCHTAB *schptr, int32 flag,
+    const char *cptr, REG *lowr, REG *highr, uint32 lows, uint32 highs);
 t_stat eval_cmd (int32 flag, const char *ptr);
 t_stat load_cmd (int32 flag, const char *ptr);
 t_stat run_cmd (int32 flag, const char *ptr);

tests/unit/src/core/CMakeLists.txt

@@ -22,6 +22,14 @@ add_unit_test(unit-scp-unit
         ${PROJECT_SOURCE_DIR}/tests/unit/support
 )
 
+add_unit_test(unit-scp-register
+    LABEL unit
+    SOURCES
+        ${CMAKE_CURRENT_SOURCE_DIR}/test_scp_register.c
+    INCLUDES
+        ${PROJECT_SOURCE_DIR}/tests/unit/support
+)
+
 add_unit_test(unit-scp-context
     LABEL unit
     SOURCES

tests/unit/src/core/test_scp_register.c

@@ -0,0 +1,58 @@
+#include <stddef.h>
+#include <setjmp.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <cmocka.h>
+
+#include "scp.h"
+#include "test_support.h"
+
+static uint8 register_buffer[4];
+static REG test_registers[] = {
+    {BRDATA(RBUF, register_buffer, 8, 8, 4)},
+    {NULL},
+};
+
+/* Verify summarized array output keeps skipped entries at their own value. */
+static void test_examine_array_register_summarizes_single_repeat(void **state)
+{
+    FILE *stream;
+    char *text = NULL;
+    size_t size = 0;
+    t_value eval[1] = {0};
+    t_value *saved_eval = sim_eval;
+
+    (void)state;
+
+    sim_eval = eval;
+    register_buffer[0] = 0;
+    register_buffer[1] = 0;
+    register_buffer[2] = 1;
+    register_buffer[3] = 0;
+
+    stream = tmpfile();
+    assert_non_null(stream);
+    assert_int_equal(exdep_reg_loop(stream, NULL, EX_E, NULL,
+                                    &test_registers[0], &test_registers[0], 0,
+                                    3),
+                     SCPE_OK);
+    assert_int_equal(simh_test_read_stream(stream, &text, &size), 0);
+    assert_string_equal(text, "RBUF[0]:\t000\n"
+                              "RBUF[1]: same as above\n"
+                              "RBUF[2]:\t001\n"
+                              "RBUF[3]:\t000\n");
+
+    sim_eval = saved_eval;
+    fclose(stream);
+    free(text);
+}
+
+int main(void)
+{
+    const struct CMUnitTest tests[] = {
+        cmocka_unit_test(test_examine_array_register_summarizes_single_repeat),
+    };
+
+    return cmocka_run_group_tests(tests, NULL, NULL);
+}