cabal v2-install --enable-profiling does not profile

[fommil]

This is in cabal-install 2.4, even the latest commit on that branch.

In any project that can produce an executable, issue

cabal v2-install --enable-profiling

and confirm that the output binary can't produce profiling information.

e.g. (not a minimal example, just first thing that comes to hand.. this is the integration test for this app)

git clone https://github.com/symbiont-io/jaeger-flamegraph.git
cd jaeger-flamegraph
cabal v2-install --symlink-bindir=bin --enable-profiling -w ghc-8.4.4 jaeger-flamegraph
gzip -cd frontend.json.gz | bin/jaeger-flamegraph -a p1 +RTS -P -RTS | sort > frontend.trace.test

gives

jaeger-flamegraph: the flag -P requires the program to be built with -prof

Note that v2-build --enable-profiling works as expected.

[hvr]

additional note, this happens also for non-local / non-project-context v2-installs:

cabal v2-install -w ghc-8.6.4 --enable-profiling uhttpc

will ignore the --enable-profiling flag too (same with --enable-executable-profiling)

and in fact, the symlinked uhttpc-bench executable is the very same (i.e. same nix-style hash entry) that

cabal v2-install -w ghc-8.6.4 uhttpc

symlinks. IOW, the 2nd invocation is a no-op.

[jneira]

Closing as duplicate of #7297 where there is a diagnostic, possible solutionand workarounds