Re: Lack of error message from invalid CROSS_COMPILER_TARGET_ARCHS

["Wells, Alex \(DLSLtd,RAL,TEC\) via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Andrew,

Thank you, that patch does exactly cover the issue I ran into. I would suggest it is worth merging as it may save others similar pains in the future.

The only other error messages I can suggest would be "Target architecture $(archPart) not defined in EPICS BASE $(path-to-config-dir)".

Thanks again,

Alex Wells

---

From: Johnson, Andrew N. <anj at anl.gov>
Sent: Tuesday, March 24, 2026 8:08 PM
To: Wells, Alex (DLSLtd,RAL,TEC) <alex.wells at diamond.ac.uk>; tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: Lack of error message from invalid CROSS_COMPILER_TARGET_ARCHS

 

Hi Alex,

Excellent question, I’m sorry to hear about the time you wasted discovering the problem.

The simple answer is probably because the Core developers working on the build didn’t think about catching that particular failure mode. Thanks for reporting this!

I can offer the patch below which will catch a completely missing target:

$ make CROSS_COMPILER_TARGET_ARCHS=linux-68040
../configure/RULES_ARCHS:67: *** Target architecture linux-68040 not supported.  Stop.

It won’t help though if the target's configure/os/CONFIG.Common.* file exists but it isn’t buildable on the current host architecture, that will fail later on in the build. The build system only requires this one file to be present for each target, all other CONFIG files are optional so I can’t easily check if the current host-target combination is valid.

diff --git a/configure/RULES_ARCHS b/configure/RULES_ARCHS

index 0d4d944d4..ebd193036 100644

--- a/configure/RULES_ARCHS

+++ b/configure/RULES_ARCHS

@@ -64,6 +64,8 @@ $(BUILD_ARCHS) : % : O.% O.Common

 $(ACTIONS) : % : $(foreach arch, $(BUILD_ARCHS), %$(DIVIDER)$(arch))

 

 $(buildDirs):

+       $(if $(wildcard $(CONFIG)/os/CONFIG.Common.$(archPart)),, \

+           $(error Target architecture $(archPart) not supported))

        $(PERL) $(TOOLS)/makeMakefile.pl $@ $(TOP)/..

 

 O.Common:

Note that the source indents must start with a real tab character. If you think this is worth including as is I’ll be happy to turn it into a PR to be merged. Suggestions for a better error message than “not supported” would be welcomed, that doesn’t seem quite right.

- Andrew

-- 

Complexity comes for free, Simplicity you have to work for.

On 3/24/26, 10:16 AM, "Tech-talk" <tech-talk-bounces at aps.anl.gov> wrote:

Hello Tech Talk,

I'm looking for some information as to why there's no obvious error message when specifying a CROSS_COMPILER_TARGET_ARCHS value that is not defined in your EPICS base installation. I would have expected there to be some kind of error message during compilation time, as EPICS obviously cannot compile my application for a platform it knows nothing about.

I do observe that a folder titled "O.<invalid platform>" is created, and populated with a Makefile that has the same format as a valid platform - the only difference is the "T_A=<platform>" parameter is changed to the non-existent one. I do see that the Make process does go into the directory and run the file, but the build system reports "nothing to be done for 'install'".

I ask this as I spent a few hours debugging why my application wasn't building. It turns out our new EPICS base installation was not configured for "linux-arm_elhf" builds.

Thank you for any information,

Alex Wells

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