Trying to debug a testsuite failure

[Jeff Law]

On 10/23/18 11:05 AM, Paul Koning wrote:
> 
> 
>> On Oct 23, 2018, at 6:08 AM, Richard Biener <richard.guenther@gmail.com> wrote:
>>
>> On Tue, Oct 23, 2018 at 2:39 AM Paul Koning <paulkoning@comcast.net> wrote:
>>>
>>> In running the gcc testsuite on pdp11, I get some failures like this:
>>>
>>> collect2: fatal error: /Users/pkoning/Documents/svn/buildpdp/gcc/nm returned 1 exit status
>>> compilation terminated.
>>> compiler exited with status 1
>>> FAIL: gcc.c-torture/execute/builtins/memcpy-chk.c compilation,  -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions
>>>
>>> While those tests flags are not terribly useful on a small memory platform like pdp11, I wouldn't expect a failure like that.  Some tests with those flags do pass.
>>>
>>> The real issue is that collect2 is apparently failing for no visible reason and without any helpful explanation of what it's trying to do.  Any hints on how I might debug this?
>>
>> Try with -Wl,-debug -Wl,-v but then it already tells you that nm
>> failed somehow.  So possibly debug
>> that via strace -f?
>>
>> Richard.
> 
> Found the problem.  By default (without a suitable linker script) the linker does not report memory overflow.  The failing cases are all programs too large to fit in the 16 bit address space of the target.  
> 
> I changed the board file to specify a linker script with explicit memory bounds, and a torture options override that omits the -O3 variants.  Now I get sane results.
> 
Yea.  You also have to watch out for things which fit in the memory map
statically but where your stack/heap will collide at runtime.  I saw
this all the time when I used to do embedded work on 16 bit targets.

jeff