llvm dev - Jan 2015 - [LLVMdev] debugging opt passed using gdb: could not open input file

Hi all,

I would like to be able to debug opt passes.
- I compiled llvm in debug mode
- gdb /usr/local/bin/opt
- run opt -load /path/to/LLVMHello.so -hello <any.bc> /dev/null

and then get /usr/local/bin/opt: opt: err: Could not open input file ....

could it be the <> syntax is not gdb command window conform?
I tried to find out if i could provide opt in and out files using standard 
parameter (like opt -i or something), but there seems to be none.

So how could I correctly invoke opt in gdb? 

Thx
Alex

Hi Alex,

2015-01-12 9:14 GMT+01:00 Alexander Poddey <alexander.poddey at
gmx.net>:
> Hi all,
>
> I would like to be able to debug opt passes.
> - I compiled llvm in debug mode
> - gdb /usr/local/bin/opt
> - run opt -load /path/to/LLVMHello.so -hello <any.bc> /dev/null
>
> and then get /usr/local/bin/opt: opt: err: Could not open input file ....
I think that one problem is that you have "opt" after "run"
in your
command. Another detail I noticed is that you are lacking an equals
sign between the "-load" and the plugin filename compared to the opt
documentation.

For your example it would be:
run -load=/path/to/LLVMHello.so -hello < any.bc > /dev/null
>
> could it be the <> syntax is not gdb command window conform?
> I tried to find out if i could provide opt in and out files using standard
> parameter (like opt -i or something), but there seems to be none.
>
> So how could I correctly invoke opt in gdb?
I think that it will work to specify your in and out files using I/O
redirection with the changes described above. If you can't get that to
work you can try:
opt -load=/path/to/LLVMHello.so -hello -o=output.bc input.bc

I haven't got access to gdb and opt at the moment so I can't try the
suggestions myself but I hope they are correct.

Best regards
David
>
> Thx
> Alex
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Hi David,

my first follow-up got lost, therefore in short again:

using backticks solves the problem:
run `opt -load=/pathTo/LLVMHello.so  -hello < /pathTo/your.bc > /dev/null`

using -load /path was mentioned in the docu, although opt -help states 
-load=/path; this however did not solve the issue.

Thanks for your advice!
Alex