WIP: Sketch interpose-memreader command for lldb-test #1
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vedantk
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Oct 13, 2020
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 swiftlang#2 0x0000000804916229 in abort () at /usr/src/lib/libc/stdlib/abort.c:67 swiftlang#3 0x000000000451b5f5 in fatalUncheckedError () at /usr/src/contrib/llvm-project/llvm/lib/Support/Error.cpp:112 swiftlang#4 0x00000000019cf008 in GetEntryPointAddress () at /usr/src/contrib/llvm-project/llvm/include/llvm/Support/Error.h:267 swiftlang#5 0x0000000001bccbd8 in ConstructorSetup () at /usr/src/contrib/llvm-project/lldb/source/Target/ThreadPlanCallFunction.cpp:67 swiftlang#6 0x0000000001bcd2c0 in ThreadPlanCallFunction () at /usr/src/contrib/llvm-project/lldb/source/Target/ThreadPlanCallFunction.cpp:114 swiftlang#7 0x00000000020076d4 in InferiorCallMmap () at /usr/src/contrib/llvm-project/lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp:97 swiftlang#8 0x0000000001f4be33 in DoAllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp:604 swiftlang#9 0x0000000001fe51b9 in AllocatePage () at /usr/src/contrib/llvm-project/lldb/source/Target/Memory.cpp:347 swiftlang#10 0x0000000001fe5385 in AllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Target/Memory.cpp:383 swiftlang#11 0x0000000001974da2 in AllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Target/Process.cpp:2301 swiftlang#12 CanJIT () at /usr/src/contrib/llvm-project/lldb/source/Target/Process.cpp:2331 swiftlang#13 0x0000000001a1bf3d in Evaluate () at /usr/src/contrib/llvm-project/lldb/source/Expression/UserExpression.cpp:190 swiftlang#14 0x00000000019ce7a2 in EvaluateExpression () at /usr/src/contrib/llvm-project/lldb/source/Target/Target.cpp:2372 swiftlang#15 0x0000000001ad784c in EvaluateExpression () at /usr/src/contrib/llvm-project/lldb/source/Commands/CommandObjectExpression.cpp:414 swiftlang#16 0x0000000001ad86ae in DoExecute () at /usr/src/contrib/llvm-project/lldb/source/Commands/CommandObjectExpression.cpp:646 swiftlang#17 0x0000000001a5e3ed in Execute () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandObject.cpp:1003 swiftlang#18 0x0000000001a6c4a3 in HandleCommand () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:1762 swiftlang#19 0x0000000001a6f98c in IOHandlerInputComplete () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:2760 swiftlang#20 0x0000000001a90b08 in Run () at /usr/src/contrib/llvm-project/lldb/source/Core/IOHandler.cpp:548 swiftlang#21 0x00000000019a6c6a in ExecuteIOHandlers () at /usr/src/contrib/llvm-project/lldb/source/Core/Debugger.cpp:903 swiftlang#22 0x0000000001a70337 in RunCommandInterpreter () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:2946 swiftlang#23 0x0000000001d9d812 in RunCommandInterpreter () at /usr/src/contrib/llvm-project/lldb/source/API/SBDebugger.cpp:1169 swiftlang#24 0x0000000001918be8 in MainLoop () at /usr/src/contrib/llvm-project/lldb/tools/driver/Driver.cpp:675 swiftlang#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 (cherry picked from commit 1ce07cd)
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