Allow GHC defaults to be modified with an environment variable

I wanted to do this to turn -fsimple-list-literals on and off for NoFib without editing a million makefiles or recompiling GHC, but I bet there are other reasons. GHC's validate should probably prompt the user to verify they want to continue of the variable is set, and should issue a loud warning at the very end indicating what options were set by the variable.

Trac metadata

Trac field	Value
Version	7.8.2
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
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Blocking
CC
Operating system
Architecture

changed weight to 5

added Tfeature request Trac import labels

Might be simpler to just patch NoFib to read off an ENV Var for additional flags, have you dug into doing that? I'm happy to help you figure out a patch for that. Much simpler (and safer) than patching ghc to read off env vars always

I think https://github.com/ghc/nofib/blob/master/mk/ghc-opts.mk is all you need to modify to change the flags passed everywhere.

edit: reading more closely, that file says its not the place where additional options should be added, BUT one of those files in the mk directory should suite

changed weight to 0

Trac metadata

Trac field	Value
Priority	normal → lowest

Someone who understands the build system might be able to tell you.

Trac metadata

Trac field	Value
Component	Compiler → Build System

closed

Replying to [ticket:9500#comment:90975 thomie]:

Someone who understands the build system might be able to tell you.

That would be me now.

The documentation says to use EXTRA_HC_OPTS. I checked, and that should indeed work. Please reopen if it doesn't.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

The new Hadrian build system has been merged. Relabeling the tickets concerning the legacy make build system to prevent confusion.

Trac metadata

Trac field	Value
Component	Build System → Build System (make)

added Plow label