I'm porting some C++ code to Android using NDK and GCC. The code basically runs. At one point, when debugging in Eclipse, the call
Dabbler::Android::Factory* pFactory = new Dabbler::Android::Factory;causes this error:
Thread [1] (Suspended: Signal 'SIGILL' received. Description: Illegal instruction.) 1 <symbol is not available> 0x812feb44What does that mean? Has the compiler generated illegal code for some reason? I have a breakpoint in the constructor (which does nothing), and it's not hit. I have already done a full rebuild.
What could I be doing wrong to cause this problem?
Best Answer
Make sure that all functions with non-void return type have a return statement.
While some compilers automatically provide a default return value, others will send a SIGILL or SIGTRAP at runtime when trying to leave a function without a return value.
It means the CPU attempted to execute an instruction it didn't understand. This could be caused by corruption I guess, or maybe it's been compiled for the wrong architecture (in which case I would have thought the O/S would refuse to run the executable). Not entirely sure what the root issue is.
It could be some un-initialized function pointer, in particular if you have corrupted memory (then the bogus vtable of C++ bad pointers to invalid objects might give that).
BTW gdb watchpoints & tracepoints, and also valgrind might be useful (if available) to debug such issues. Or some address sanitizer.
LeetCode's online compiler and dev environment generates SIGILL errors for mistakes that do not generate the same error in my desktop IDE.
For example, array access with an out-of-bounds index:
["foo", "bar"][2]LeetCode's compiler shows only the error:
Runtime Errorprocess exited with signal
SIGILL
in a local Xcode playground this same code instead results in the error:
error: Execution was interrupted, reason: EXC_BREAKPOINT (code=1, subcode=0x18f2ea5d8).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.
Only in a full Xcode project compilation and run does it report the actual error:
Thread 1: Fatal error: Index out of range