Add new file, vm_debug.c, and help command for it

include/vm_debug.h

@@ -0,0 +1,60 @@
+#ifndef _VM_DEBUG_H_
+#define _VM_DEBUG_H_
+
+typedef struct {
+    /*
+     * Most commands that need an argument will simply use addr1, but a
+     * few have more than one address--hence addr2.
+     */
+    int addr1;
+    int addr2;
+
+    /*
+     * If we have a thing we want to work with, but want to leave what
+     * that is up to the helper func, then you can write it into the
+     * target.
+     *
+     * If a command uses target, followed by an address, that address
+     * will be in addr1.
+     */
+    char target[256];
+} vm_debug_args;
+
+typedef void (*vm_debug_func)(vm_debug_args *);
+
+typedef struct {
+    /*
+     * The name field is the full name of the command; each command also
+     * has an abbreviated form (either is acceptable as input), which is
+     * defined in the abbrev field.
+     */
+    char *name;
+    char *abbrev;
+
+    /*
+     * The number of arguments we expect to see
+     */
+    int nargs;
+
+    /*
+     * The function that will do something with the command's input
+     */
+    vm_debug_func handler;
+
+    /*
+     * What do our arguments look like?
+     */
+    char *argdesc;
+
+    /*
+     * What do we do?
+     */
+    char *desc;
+} vm_debug_cmd;
+
+#define DEBUG_CMD(x) \
+    void vm_debug_cmd_##x (vm_debug_args *args)
+
+extern DEBUG_CMD(help);
+
+#endif

sources.cmake

@@ -25,6 +25,7 @@ set(erc_sources
 	option.c
 	vm_area.c
 	vm_bitfont.c
+	vm_debug.c
 	vm_di.c
 	vm_event.c
 	vm_reflect.c

src/vm_debug.c

@@ -0,0 +1,27 @@
+/*
+ * vm_debug.c
+ */
+
+#include <stdio.h>
+
+#include "vm_debug.h"
+#include "vm_di.h"
+
+vm_debug_cmd cmdtable[] = {
+    { "help", "h", 0, vm_debug_cmd_help, "",
+        "Print out this list of commands", },
+};
+
+#define CMDTABLE_SIZE (sizeof(cmdtable) / sizeof(vm_debug_cmd))
+
+DEBUG_CMD(help)
+{
+    FILE *stream = (FILE *)vm_di_get(VM_OUTPUT);
+    vm_debug_cmd *cmd;
+    
+    for (int i = 0; i < CMDTABLE_SIZE; i++) {
+        cmd = &cmdtable[i];
+        fprintf(stream, "%-15s%-5s%-15s%s\n", cmd->name, cmd->abbrev, 
+                cmd->argdesc, cmd->desc);
+    }
+}

tests/vm_debug.c

@@ -0,0 +1,47 @@
+#include <criterion/criterion.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "vm_debug.h"
+#include "vm_di.h"
+
+static char buf[BUFSIZ];
+static FILE *stream = NULL;
+static vm_debug_args args;
+
+static void
+setup()
+{
+    // Don't worry...we don't care about /dev/null, because we'll hijack
+    // the output with setvbuf below
+    stream = fopen("/dev/null", "w");
+    if (stream == NULL) {
+        perror("Could not open /dev/null for stream testing");
+        exit(1);
+    }
+
+    vm_di_set(VM_OUTPUT, stream);
+
+    // Writing to stream will now write to buf
+    setvbuf(stream, buf, _IOFBF, BUFSIZ);
+}
+
+static void
+teardown()
+{
+    memset(buf, 0, BUFSIZ);
+    fclose(stream);
+}
+
+TestSuite(vm_debug, .init = setup, .fini = teardown);
+
+/*
+ * I dunno what we'll end up printing! It'll change as we add commands,
+ * so we just test if we print _something_.
+ */
+Test(vm_debug, cmd_help)
+{
+    vm_debug_cmd_help(&args);
+    cr_assert_neq(strlen(buf), 0);
+    printf("%s", buf);
+}