SBThread::StepInstruction shouldn't discard other plans (#97493)

This was just a typo, none of the external execution control functions
should discard other plans. In particular, it means if you stop in a
hand-called function and step an instruction, the function call thread
plan gets unshipped, popping all the function call frames.

I also added a test that asserts the correct behavior. I tested all the
stepping operations even though only StepInstruction was wrong.

1 files changed, 10 insertions, 0 deletions

diff --git a/lldb/test/API/python_api/thread/main.cpp b/lldb/test/API/python_api/thread/main.cpp
index dde740a1b6bf..d4b0ad2372c3 100644
--- a/lldb/test/API/python_api/thread/main.cpp
+++ b/lldb/test/API/python_api/thread/main.cpp
@@ -5,8 +5,18 @@
 char my_char = 'u';
 int my_int = 0;
 
+void
+call_me(bool should_spin) {
+    int counter = 0;
+    if (should_spin) {
+        while (1)
+            counter++;  // Set a breakpoint in call_me
+     }
+}
+
 int main (int argc, char const *argv[])
 {
+    call_me(false);
     for (int i = 0; i < 3; ++i) {
         printf("my_char='%c'\n", my_char);
         ++my_char;