Re: Multigot mechanism and a related MIPS linker error

[Nick Clifton <nickc at redhat dot com>]

Hi Shankar,

> For our MIPS cross-compiler,
> gcc version is  4.2.0
> binutils version is 2.17.90.

I assume that you know that 2.17.90 is an old binutils release ?  We are 
currently on release 2.19 and 2.20 will be out shortly.


I am not a MIPS expert, so I am not going to try to answer your 
questions about the multigot feature, but I can answer this question:

> d) I want to understand the ld test-suite
> (/toolchain/testsuite/binutils/testsuite/ld/ld-mips-elf)  Is there any
> writeup  somewhere ?

There is no writeup.  (Maybe someone would like to create one ?)  In 
essence though the linker tests are meant to be self-documenting.

What happens is that in each sub-directory of the testsuite there are 
one or more "expect" files.  These are files that have the .exp 
extension.  They are written in a scripting language called expect. 
(http://en.wikipedia.org/wiki/Expect).  These files decide which tests 
should be run based on the target being tested, and occasionally they 
contain extra code to help with the testing.  Some helper code can also 
be found in the ld/testsuite/lib/ld-lib.exp file.

Most individual linker tests consist of one or more assembler or C 
source files (with .s or .c extensions) and also an expected output file 
(with a .d extension).  The .d file actually drives the test.  At the 
start of the file are various directives which specify things like the 
name of the test, the source files that must be assembled or compiled 
first, the command line options to pass to the linker, the program used 
to examine the output of the linker and so on.

Ideally each test will check just one particular feature of the linker, 
or make sure that one particular bug is no longer present in the linker. 
 Also the tests should be separated into sub-directories based on the 
target that they are for or the general area of the linker that they are 
testing.  Hence the ld-mips-elf sub-directory contains tests for MIPS 
linkers that use the ELF file format.

The testsuite itself is run using another tool called DejaGnu 
(http://en.wikipedia.org/wiki/Dejagnu).  Apart from setting up a 
site.exp file and DEJAGNU environment variable before using dejagnu for 
the first time, most testers will not need to deeply into the internals 
of DejaGnu.

I hope that this explanation helps.

Cheers
  Nick