[LLVMdev] Advice on debugging?

Talin viridia at gmail.com
Fri Mar 28 18:07:46 PDT 2008

I've been using lli to do most of my unit tests for the compiler that 
I'm writing. However, when I get a test that crashes, its difficult to 
find which instruction it was that caused the crash. I tried running 
bugpoint, but it didn't seem to work for me, and upon reading the 
documentation, it seems to be intended for a different purpose than 
finding bugs in my source program; It seems to be related more to 
finding errors in the various optimizer passes.

So for example, when I run lli on my program:
Assertion failed: (V == V2 && "Didn't find key?"), function RemoveKey, 
file StringMap.cpp, line 177.
0   lli                                 0x0049edcd 
_ZN40_GLOBAL__N_Signals.cpp_00000000_B58D0A3815PrintStackTraceEv + 45
1   lli                                 0x0049efc9 
_ZN40_GLOBAL__N_Signals.cpp_00000000_B58D0A3813SignalHandlerEi + 323
2   libSystem.B.dylib                   0x9534297b _sigtramp + 43
3   ???                                 0xffffffff 0x0 + 4294967295
4   libSystem.B.dylib                   0x953bb782 raise + 26
5   libSystem.B.dylib                   0x953cad3f abort + 73
6   libSystem.B.dylib                   0x953bc923 __assert_rtn + 101
7   lli                                 0x00491ca7 
_ZN4llvm13StringMapImpl9RemoveKeyEPNS_18StringMapEntryBaseE + 127
8   lli                                 0x00461946 
+ 24
9   lli                                 0x00461094 
+ 24
10  lli                                 0x0040aabe 
+ 94
11  lli                                 0x003cbd66 
+ 254

But when I run bugpoint, I get:
Read input file      : 'out/Debug/test/stdlib/test08.bcc'
*** All input ok
Found gcc: /usr/bin/gcc
Initializing execution environment: Running the code generator to test 
for a crash: <cbe>
Generating reference output from raw program: 
<cbe><cbe><gcc><program>Reference output is: bugpoint.reference.out

*** Checking the code generator...
*** Debugging miscompilation!
Checking to see if '' compile correctly: <cbe><gcc><program> yup.
*** Optimized program matches reference output!  No problem detected...
bugpoint can't help you with your problem!

To be honest, I am not sure what this all means.

In any case, what I'd like is a way to find out more about the source of 
the crash.

I don't suppose anyone is working on a version of lli that supports 
single-step debugging from the command line? Or do I need to compile to 
assembly and use gdb? What's the best strategy for solving this type of 

-- Talin

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