Re: [PATCH] elf/tests: Make thrlock and noload depend on libm

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

On 7/8/21 11:16 AM, Florian Weimer wrote:
> * Siddhesh Poyarekar:
> 
>> On 7/7/21 10:36 PM, Florian Weimer via Libc-alpha wrote:
>>> * Siddhesh Poyarekar via Libc-alpha:
>>>
>>>> Both tests try to dlopen libm.so at runtime, so make them depend on it
>>>> to avoid running before libm.so is built.
>>> Can that really happen in the current build system?
>>
>> I don't the exact sequence of events, but I did run into this a few
>> minutes ago, which is how I realized there was a missing dependency.
>> The tests failed with "file too short", which was probably them racing
>> with the static linker linking libm.so.
> 
> Hmm.  I would expect that recursive make running in elf subdirectory
> simply does not have the knowledge how to link libm properly.  And it
> will definitely not do that while running tests.

My mental model of how this works is that make builds dependency trees 
and then runs independent trees in parallel.  In that model, if tests 
don't have that dependency, they may end up in a different dependency 
tree from that of libm and both could then happen in parallel.  Of 
course, I don't actually know if that's how make works because I haven't 
read the sources.

Oh, and running only tests (assuming that all built objects are up to 
date) won't do this.  It'll only happen if some object needs to be 
updated when the test is run because an undercaffeinated developer ran 
make check instead of make && make check :)

Siddhesh