Don't set a software stepping breakpoint at 0 on arm.

[labath]

Summary

Added a test for the next_pc being zero before setting a software breakpoint
in arm32.
Reenabled the crash during step test for android/linux.

[jingham]

Not commenting on the substance of the change (though it seems sensible to me.) The inclusion of the .gitignore was probably accidental, but in any case, try not to gang unrelated changes together like this. Thanks!

[labath]

I envisioned a bit different solution to this problem. The issue does not happen only when the inferior jumps to a literal 0x0 address, but for any address that is not mapped into memory (so we cannot set a breakpoint there). The simplest way to figure out whether we are able to set a breakpoint is to actually try setting it, and check for the error. (plus, I don't think your code handles the thumb case)

And yes, the .gitignore changes should not be a part of this change. :)

.gitignore

 # Byte compiled python modules.
 *.pyc
 *.pyproj
 # pyenv settings
 .python-version
 *.sln
 *.suo
 # vim swap files
-.*.swp
+.*.sw?
 .sw?
 # OS X specific files.
 .DS_store
 DerivedData/
 
 # Remote build configuration files.
 .remote-build.conf
 
 build/
 pyproj/
 llvm-build/
 ninja/
 *xcuserdata
 test/20*
 __pycache__/
 *.lock
 *.so
+a.out
+*.o
+*.d
+*.dwo
 
+.ycm_extra_conf.py
 clang-module-cache
 
 # Skip ctags-style tags files
 tags
 
 # We should ignore Xcode-style embedding of llvm/ at lldb root dir.
 # Do not add trailing '/'s, they skip symlinks.
 /llvm

packages/Python/lldbsuite/test/functionalities/thread/crash_during_step/TestCrashDuringStep.py

class CreateDuringStepTestCase(TestBase):
 
     mydir = TestBase.compute_mydir(__file__)
 
     def setUp(self):
         TestBase.setUp(self)
         self.breakpoint = line_number('main.cpp', '// Set breakpoint here')
 
     @expectedFailureAll(oslist=["windows"], bugnumber="llvm.org/pr24778")
-    @expectedFailureAndroid("llvm.org/pr24497", archs=['arm', 'aarch64'])
-    @expectedFailureAll(
-        oslist=["linux"],
-        archs=["arm"],
-        bugnumber="llvm.org/pr24497")
     # IO error due to breakpoint at invalid address
     @expectedFailureAll(triple=re.compile('^mips'))
     def test_step_inst_with(self):
         """Test thread creation during step-inst handling."""
         self.build(dictionary=self.getBuildFlags())
         exe = os.path.join(os.getcwd(), "a.out")
 
         target = self.dbg.CreateTarget(exe)

source/Plugins/Process/Linux/NativeProcessLinux.cpp

if (emulation_result) {
     // modifying the PC but we don't  know how.
     return Error("Instruction emulation failed unexpectedly.");
   }
 
   if (m_arch.GetMachine() == llvm::Triple::arm) {
     if (next_flags & 0x20) {
       // Thumb mode
       error = SetSoftwareBreakpoint(next_pc, 2);
-    } else {
+    } else if (next_pc) {
       // Arm mode
       error = SetSoftwareBreakpoint(next_pc, 4);
     }
   } else if (m_arch.GetMachine() == llvm::Triple::mips64 ||
              m_arch.GetMachine() == llvm::Triple::mips64el ||
              m_arch.GetMachine() == llvm::Triple::mips ||
              m_arch.GetMachine() == llvm::Triple::mipsel)
     error = SetSoftwareBreakpoint(next_pc, 4);