6200 - --dump is not needed for incremental traces

This undoes commit 5764, which was ill-considered. We already had incremental
prints at that point to 'last_run'. As long as we don't run out of RAM
on large traces, there doesn't seem any need to print to stderr.

Now '--dump' is only needed when juggling multiple traces.

001help.cc

@@ -81,13 +81,9 @@ void init_help() {
     "== Debugging aids\n"
     "- Add '--trace' to any of these commands to save a trace to disk at the end.\n"
     "  This can run out of memory for long-running commands.\n"
-    "- Add '--debug' to add information to traces. 'bootstrap --debug translate'\n"
-    "  will save metadata to disk that 'bootstrap --trace run' uses to make traces\n"
-    "  more informative.\n"
-    "- Add '--dump --trace' to emit a trace incrementally to stderr.\n"
-    "  This approach will work even for long-running programs.\n"
-    "  (Though the combination of flags is counter-intuitive and can probably\n"
-    "  be improved.)\n"
+    "- Add '--debug' to emit additional debug information during translation.\n"
+    "  'bootstrap --debug translate' will save metadata to disk that\n"
+    "  'bootstrap --trace run' uses to make traces more informative.\n"
     "\n"
     "Options starting with '--' must always come before any other arguments.\n"
     "\n"

003trace.cc

@@ -190,8 +190,6 @@ void trace_stream::newline() {
     if (should_incrementally_print_trace()) {
       dump_trace_line(cerr, t);
     }
-    // Hack: on 'bootstrap --trace --dump', emit only to stderr, not 'last_run'.
-    if (Dump_trace) past_lines.pop_back();  // economize on memory
     // End trace Commit
   }
 
@@ -458,6 +456,7 @@ else if (is_equal(*arg, "--trace")) {
 :(before "End trace Commit")
 if (Trace_file) {
   dump_trace_line(Trace_file, t);
+  past_lines.pop_back();  // economize on memory
 }
 :(before "End One-time Setup")
 atexit(cleanup_main);

README.md

@@ -470,7 +470,7 @@ rudimentary but hopefully still workable toolkit:
   `./translate_subx_debug`, and then running:
 
   ```
-  ./bootstrap --debug --trace --dump run a.elf test 2>&1 |grep 'label test'
+  ./bootstrap --trace --dump run a.elf test 2>&1 |grep 'label test'
   ```
 
   Just read out the last test printed out before the segfault.

run_one_test

@@ -20,4 +20,5 @@ fi
 set -e
 
 ./translate_subx_debug init.linux $(echo $FILES) /tmp/run_one_test.subx
-CFLAGS=$CFLAGS ./bootstrap --debug --trace run a.elf
+echo running
+CFLAGS=$CFLAGS ./bootstrap --trace run a.elf