llvm dev - Jun 2008 - [LLVMdev] LLVM on OpenBSD

On Tue, Jun 17, 2008 at 4:56 PM, Edd Barrett <vext01 at gmail.com>
wrote:
> On Tue, Jun 17, 2008 at 4:51 PM, Edd Barrett <vext01 at gmail.com>
wrote:
>> I am trying the same with gcc-4.2 now.
>
> The above results were infact with gcc-4.2. My apologies.
With 3.3.5 my first test took 5 times to produce a non "bus error"
build. There were no 'make cleans' in between.

What is going on?

-- 

Best Regards

Edd

http://students.dec.bournemouth.ac.uk/ebarrett

> With 3.3.5 my first test took 5 times to produce a non "bus
> error" build. There were no 'make cleans' in between.
>
> What is going on?
You mean you used your bsd-ports-provided gcc to compile LLVM and 
you've got 4 times a bus-error during the build?  In this case, 
it cannot be a LLVM problem.

In the linux-community, people say that bus-error's are almost 
always because of faulty hardware, e.g. problem with DRAM 
timing, overheated CPU, power-supply that cannot provide enought 
power during current surges, things like that.

On Jun 18, 2008, at 12:20 AM, Holger Schurig wrote:
> In the linux-community, people say that bus-error's are almost
> always because of faulty hardware, e.g. problem with DRAM
> timing, overheated CPU, power-supply that cannot provide enought
> power during current surges, things like that.

At least bus errors that aren't reproducible are likely caused by  
this. It could be random memory corruption or a bug in the host  
compiler - then again that compiler is > 8 years old at this point?

-eric

Holger Schurig wrote:
>> With 3.3.5 my first test took 5 times to produce a non "bus
>> error" build. There were no 'make cleans' in between.
>>
>> What is going on?
> 
> You mean you used your bsd-ports-provided gcc to compile LLVM and 
> you've got 4 times a bus-error during the build?  In this case, 
> it cannot be a LLVM problem.
Ok, to clarify,

I have tried the OpenBSD provided gcc-3.3.5 (which is considered the
least buggy version of gcc) and also with gcc-4.2 from ports.

Sometimes you get a clean build of llvm, sometimes you don't and instead
get a bus error.
> 
> In the linux-community, people say that bus-error's are almost 
> always because of faulty hardware, e.g. problem with DRAM 
> timing, overheated CPU, power-supply that cannot provide enought 
> power during current surges, things like that.
That is one reason a bus error might occur, but my more common
understanding of a bus error is data not properly aligned with the byte
boundaries and/or out of range memory at the physical level.

The machine I am building on is my workstation which I use 9-4.30
mon-fri. I run all manner of apps without any problems, so if it were
bad hardware it would have shown itself by now surely.

As a test I got another developer to try on a different machine and he 
has the same problem. In another test he  also tried a more aggressive 
malloc.conf (a mechanism which causes malloc to do all sorts of 
randomisation and page filling to test for memory based bugs) and a 
completely different error was encountered:

SelectionDAG.cpp:2602: warning: converting of negative value
`-1' to `long long

Also we found that without specifying --enable-optimized, the 
optimisations were still present:

-O3 -fomit-frame-pointer -Woverloaded-virtual -pedantic
-Wall -W -Wwrite-strings -Wno-long-long -Wunused -Wno-unused-parameter
-O3

:¬(

-- 

Best Regards
Edd

http://students.dec.bmth.ac.uk/ebarrett