[lldb] Fix `thread backtrace --count` (#83602)

The help output for `thread backtrace` specifies that you can pass -1 to
`--count` to display all the frames.

```
-c <count> ( --count <count> )
            How many frames to display (-1 for all)
```

However, that doesn't work:

```
(lldb) thread backtrace --count -1
error: invalid integer value for option 'c'
```

The problem is that we store the option value as an unsigned and the
code to parse the string correctly rejects it. There's two ways to fix
this:

1. Make `m_count` a signed value so that it accepts negative values and
appease the parser. The function that prints the frames takes an
unsigned so a negative value will just become a really large positive
value, which is what the current implementation relies on.
2. Keep `m_count` unsigned and instead use 0 the magic value to show all
frames. I don't really see a point in not showing any frames at all,
plus that's already broken (`error: error displaying backtrace for
thread: "0x0001"`).

This patch implements (2) and at the same time improve the error
reporting so that we print the invalid value when we cannot parse it.

rdar://123881767

1 files changed, 21 insertions, 12 deletions

diff --git a/lldb/source/Commands/CommandObjectThread.cpp b/lldb/source/Commands/CommandObjectThread.cpp
index 9cfff059..6d84315 100644
--- a/lldb/source/Commands/CommandObjectThread.cpp
+++ b/lldb/source/Commands/CommandObjectThread.cpp
@@ -67,13 +67,18 @@ public:
         if (option_arg.getAsInteger(0, m_count)) {
           m_count = UINT32_MAX;
           error.SetErrorStringWithFormat(
-              "invalid integer value for option '%c'", short_option);
+              "invalid integer value for option '%c': %s", short_option,
+              option_arg.data());
         }
+        // A count of 0 means all frames.
+        if (m_count == 0)
+          m_count = UINT32_MAX;
         break;
       case 's':
         if (option_arg.getAsInteger(0, m_start))
           error.SetErrorStringWithFormat(
-              "invalid integer value for option '%c'", short_option);
+              "invalid integer value for option '%c': %s", short_option,
+              option_arg.data());
         break;
       case 'e': {
         bool success;
@@ -81,7 +86,8 @@ public:
             OptionArgParser::ToBoolean(option_arg, false, &success);
         if (!success)
           error.SetErrorStringWithFormat(
-              "invalid boolean value for option '%c'", short_option);
+              "invalid boolean value for option '%c': %s", short_option,
+              option_arg.data());
       } break;
       default:
         llvm_unreachable("Unimplemented option");
@@ -228,9 +234,9 @@ protected:
           thread->GetIndexID());
       return false;
     }
-    if (m_options.m_extended_backtrace) { 
-      if (!INTERRUPT_REQUESTED(GetDebugger(), 
-                              "Interrupt skipped extended backtrace")) {
+    if (m_options.m_extended_backtrace) {
+      if (!INTERRUPT_REQUESTED(GetDebugger(),
+                               "Interrupt skipped extended backtrace")) {
         DoExtendedBacktrace(thread, result);
       }
     }
@@ -272,8 +278,9 @@ public:
       bool avoid_no_debug =
           OptionArgParser::ToBoolean(option_arg, true, &success);
       if (!success)
-        error.SetErrorStringWithFormat("invalid boolean value for option '%c'",
-                                       short_option);
+        error.SetErrorStringWithFormat(
+            "invalid boolean value for option '%c': %s", short_option,
+            option_arg);
       else {
         m_step_in_avoid_no_debug = avoid_no_debug ? eLazyBoolYes : eLazyBoolNo;
       }
@@ -284,8 +291,9 @@ public:
       bool avoid_no_debug =
           OptionArgParser::ToBoolean(option_arg, true, &success);
       if (!success)
-        error.SetErrorStringWithFormat("invalid boolean value for option '%c'",
-                                       short_option);
+        error.SetErrorStringWithFormat(
+            "invalid boolean value for option '%c': %s", short_option,
+            option_arg);
       else {
         m_step_out_avoid_no_debug = avoid_no_debug ? eLazyBoolYes : eLazyBoolNo;
       }
@@ -293,8 +301,9 @@ public:
 
     case 'c':
       if (option_arg.getAsInteger(0, m_step_count))
-        error.SetErrorStringWithFormat("invalid step count '%s'",
-                                       option_arg.str().c_str());
+        error.SetErrorStringWithFormat(
+            "invalid integer value for option '%c': %s", short_option,
+            option_arg.data());
       break;
 
     case 'm': {