Re: [PATCH v2] testsuite: Only run test on target if VMA == LMA

[Richard Sandiford <richard.sandiford@arm.com>]

Sorry for the slow reply.

Torbjorn SVENSSON <torbjorn.svensson@foss.st.com> writes:
> Hi Richard,
>
> Thanks for your review.
> Comments below.
>
> On 2022-09-23 19:34, Richard Sandiford wrote:
>> Torbjörn SVENSSON via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
>>> Checking that the triplet matches arm*-*-eabi (or msp430-*-*) is not
>>> enough to know if the execution will enter an endless loop, or if it
>>> will give a meaningful result. As the execution test only work when
>>> VMA and LMA are equal, make sure that this condition is met.
>>>
>>> 2022-09-16  Torbjörn SVENSSON  <torbjorn.svensson@foss.st.com>
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> 	* lib/target-supports.exp (check_effective_target_vma_equals_lma): New.
>>>          * c-c++-common/torture/attr-noinit-1.c: Requre VMA == LMA to run.
>>>          * c-c++-common/torture/attr-noinit-2.c: Likewise.
>>>          * c-c++-common/torture/attr-noinit-3.c: Likewise.
>>>          * c-c++-common/torture/attr-persistent-1.c: Likewise.
>>>          * c-c++-common/torture/attr-persistent-3.c: Likewise.
>> 
>> Looks like a nice thing to have.
>> 
>> Could you add an entry to doc/sourcebuild.texi too?
>
> I've added a note and will be shared in a v3.
>
>>> +
>>> +            # Example output of objdump:
>>> +            #vma_equals_lma9059.exe:     file format elf32-littlearm
>>> +            #
>>> +            #Sections:
>>> +            #Idx Name          Size      VMA       LMA       File off  Algn
>>> +            #  6 .data         00000558  20000000  08002658  00020000  2**3
>>> +            #                  CONTENTS, ALLOC, LOAD, DATA
>>> +
>>> +            # Capture LMA and VMA columns for .data section
>>> +            if ![ regexp "\d*\d+\s+\.data\s+\d+\s+(\d+)\s+(\d+)" $output dummy vma lma ] {
>> 
>> Maybe my Tcl is getting rusty, but I'm surprised this quoting works.
>> I'd have expected single backslashes to be interpreted as C-style
>> sequences (for \n etc) and so be eaten before regexp sees them.
>> Quoting with {...} instead of "..." would avoid that.
>
> Good catch! I'm not fluent in Tcl and apparently, I was not testing this 
> well enough before sending it to the list. I got the expected result for 
> the test cases, but for the wrong reason. I've correct it for the v3.
>
>>> +                verbose "Could not parse objdump output" 2
>>> +                return 0
>>> +            } else {
>>> +                return [string equal $vma $lma]
>>> +            }
>>> +	} else {
>>> +            remote_file build delete $exe
>>> +            verbose "Could not determine if VMA is equal to LMA. Assuming not equal." 2
>>> +            return 0
>>> +	}
>> 
>> Would it be more conservative to return 1 on failure rather than 0?
>> That way, a faulty test would trigger XFAILs rather than UNSUPPORTEDs,
>> with XFAILs being more likely to get attention.
>
> The main issue here is that for targets where VMA != LMA, executing the 
> tests will fall into an endless recursion loop. Well, "endless" in the 
> sense that the stack might be depleted or the test will simply timeout. 
> The test cases are designed to assume that it's safe to call _start() 
> from within main() to verify that the state of some variables tagged 
> with certain attributes are correct after a "reset".

Ah, OK.  In that case, I agree return 0 is the right choice.

>> On the other hand, I suppose we don't lose much if these tests are
>> run on common targets only.  So either way is OK, just asking. ;-)
>
> Do you think it's worth to have these tests reach the timeout to have 
> them in the XFAIL list rather than in the UNSUPPORTED list?
> Keep in mind that it's not just one test case, it's 5 test cases times 
> the number of permutations of the CFLAGS...
> It's also not expected that these test cases will be changed in a way 
> that will make them work when VMA != LMA.

Yeah, good points.  Let's stick with it as it is then.

Thanks,
Richard