pkg/ifuzz: fix generate/build

[dvyukov]

Currently the commands we have in go:generate first create an empty file
and then write final contents. This breaks any parallel builds of the source.
Even running go generate ./... does not work.
Write output files atomically.

[tarasmadan]

Just curious about "(go run gen/gen.go gen/json/arm64.json | gofmt > generated/insns.tmp); mv generated/insns.tmp generated/insns.go"...

[dvyukov]

Just curious about "(go run gen/gen.go gen/json/arm64.json | gofmt > generated/insns.tmp); mv generated/insns.tmp generated/insns.go"...

This would work, but I hate duplicating non-trivial shell (we would need it in at least 3 places, probably more). Also some tools already write files in the tool, so we would need to move that code out of these tools to use bash for atomic writing.

Re hating bash: can you spot a bug in your snippet? ;)

[tarasmadan]

Just curious about "(go run gen/gen.go gen/json/arm64.json | gofmt > generated/insns.tmp); mv generated/insns.tmp generated/insns.go"...

This would work, but I hate duplicating non-trivial shell (we would need it in at least 3 places, probably more). Also some tools already write files in the tool, so we would need to move that code out of these tools to use bash for atomic writing.

Re hating bash: can you spot a bug in your snippet? ;)

You made me curious... Where? How many?

[dvyukov]

I think it should be && instead of ;.