MFC r364480:

MFC r364480:

Merge commit 1ce07cd614be from llvm git (by me):

  Instantiate Error in Target::GetEntryPointAddress() only when
  necessary

  When Target::GetEntryPointAddress() calls
  exe_module->GetObjectFile()->GetEntryPointAddress(), and the returned
  entry_addr is valid, it can immediately be returned.

  However, just before that, an llvm::Error value has been setup, but
  in this case it is not consumed before returning, like is done
  further below in the function.

  In https://bugs.freebsd.org/248745 we got a bug report for this,
  where a very simple test case aborts and dumps core:

  * thread #1, name = 'testcase', stop reason = breakpoint 1.1
      frame #0: 0x00000000002018d4 testcase`main(argc=1, argv=0x00007fffffffea18) at testcase.c:3:5
     1    int main(int argc, char *argv[])
     2    {
  -> 3        return 0;
     4    }
  (lldb) p argc
  Program aborted due to an unhandled Error:
  Error value was Success. (Note: Success values must still be checked prior to being destroyed).

  Thread 1 received signal SIGABRT, Aborted.
  thr_kill () at thr_kill.S:3
  3       thr_kill.S: No such file or directory.
  (gdb) bt
  #0  thr_kill () at thr_kill.S:3
  #1  0x00000008049a0004 in __raise (s=6) at /usr/src/lib/libc/gen/raise.c:52
  #2  0x0000000804916229 in abort () at /usr/src/lib/libc/stdlib/abort.c:67
  #3  0x000000000451b5f5 in fatalUncheckedError () at /usr/src/contrib/llvm-project/llvm/lib/Support/Error.cpp:112
  #4  0x00000000019cf008 in GetEntryPointAddress () at /usr/src/contrib/llvm-project/llvm/include/llvm/Support/Error.h:267
  #5  0x0000000001bccbd8 in ConstructorSetup () at /usr/src/contrib/llvm-project/lldb/source/Target/ThreadPlanCallFunction.cpp:67
  #6  0x0000000001bcd2c0 in ThreadPlanCallFunction () at /usr/src/contrib/llvm-project/lldb/source/Target/ThreadPlanCallFunction.cpp:114
  #7  0x00000000020076d4 in InferiorCallMmap () at /usr/src/contrib/llvm-project/lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp:97
  #8  0x0000000001f4be33 in DoAllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp:604
  #9  0x0000000001fe51b9 in AllocatePage () at /usr/src/contrib/llvm-project/lldb/source/Target/Memory.cpp:347
  #10 0x0000000001fe5385 in AllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Target/Memory.cpp:383
  #11 0x0000000001974da2 in AllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Target/Process.cpp:2301
  #12 CanJIT () at /usr/src/contrib/llvm-project/lldb/source/Target/Process.cpp:2331
  #13 0x0000000001a1bf3d in Evaluate () at /usr/src/contrib/llvm-project/lldb/source/Expression/UserExpression.cpp:190
  #14 0x00000000019ce7a2 in EvaluateExpression () at /usr/src/contrib/llvm-project/lldb/source/Target/Target.cpp:2372
  #15 0x0000000001ad784c in EvaluateExpression () at /usr/src/contrib/llvm-project/lldb/source/Commands/CommandObjectExpression.cpp:414
  #16 0x0000000001ad86ae in DoExecute () at /usr/src/contrib/llvm-project/lldb/source/Commands/CommandObjectExpression.cpp:646
  #17 0x0000000001a5e3ed in Execute () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandObject.cpp:1003
  #18 0x0000000001a6c4a3 in HandleCommand () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:1762
  #19 0x0000000001a6f98c in IOHandlerInputComplete () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:2760
  #20 0x0000000001a90b08 in Run () at /usr/src/contrib/llvm-project/lldb/source/Core/IOHandler.cpp:548
  #21 0x00000000019a6c6a in ExecuteIOHandlers () at /usr/src/contrib/llvm-project/lldb/source/Core/Debugger.cpp:903
  #22 0x0000000001a70337 in RunCommandInterpreter () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:2946
  #23 0x0000000001d9d812 in RunCommandInterpreter () at /usr/src/contrib/llvm-project/lldb/source/API/SBDebugger.cpp:1169
  #24 0x0000000001918be8 in MainLoop () at /usr/src/contrib/llvm-project/lldb/tools/driver/Driver.cpp:675
  #25 0x000000000191a114 in main () at /usr/src/contrib/llvm-project/lldb/tools/driver/Driver.cpp:890

  Fix the incorrect error catch by only instantiating an Error object
  if it is necessary.

  Reviewed By: JDevlieghere

  Differential Revision: https://reviews.llvm.org/D86355

This should fix lldb aborting as described in the scenario above.

Reported by:	dmgk
PR:		248745