kubernetes-csi / csi-driver-smb / 9088044825

79%

master: 80%

Pull #781

github

fix: Remove excessive recursive variable expansions

Modern GNU make (version >= 4.4) has backward-incompatibile feature:

> * WARNING: Backward-incompatibility!
>  Previously makefile variables marked as export were not exported to commands
>  started by the $(shell ...) function.  Now, all exported variables are
>  exported to $(shell ...).  If this leads to recursion during expansion, then
>  for backward-compatibility the value from the original environment is used.

This makes any invocation of `make` command very costly. Compare the performance of make 4.3 vs. 4.4:
```
$ time ~/Sources/make-4.3/make smb ARCH=$(go env GOARCH)
CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -ldflags "-X github.com/kubernetes-csi/csi-driver-smb/pkg/smb.driverVersion=v1.15.0 -X github.com/kubernetes-csi/csi-driver-smb/pkg/smb.gitCommit=<a class=hub.com/kubernetes-csi/csi-driver-smb/commit/f5ced814f628ddee2c9f3e6af505c5a6123e50f4">f5ced814f -X github.com/kubernetes-csi/csi-driver-smb/pkg/smb.buildDate=2024-05-15T00:00:09Z -s -w -extldflags "-static"" -mod vendor -o _output/amd64/smbplugin ./cmd/smbplugin

real	0m38.504s
user	3m50.580s
sys	0m23.502s

$ time ~/Sources/make-4.4/make smb ARCH=$(go env GOARCH)
CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -ldflags "-X github.com/kubernetes-csi/csi-driver-smb/pkg/smb.driverVersion=v1.15.0 -X github.com/kubernetes-csi/csi-driver-smb/pkg/smb.gitCommit=f5ced814f628ddee2c9f3e6af505c5a6123e50f4 -X github.com/kubernetes-csi/csi-driver-smb/pkg/smb.buildDate=2024-05-15T00:04:04Z -s -w -extldflags "-static"" -mod vendor -o _output/amd64/smbplugin ./cmd/smbplugin

real	16m59.851s
user	13m16.490s
sys	13m46.418s
```

The same variables are evaluated again and again millions times:
```
$ rpm -qf /usr/bin/make
make-4.4.1-6.fc40.x86_64

$ /usr/bin/make -d smb ARCH=$(go env GOARCH) 2>&1 |grep "not recursively expanding.*to export to shell function" |wc -l
2171342
```

The patch doesn't change user-visible behavior of Makefile, but makes `make` command as performant as it used to be in case of make 4.3.

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