compile_native_go_fuzzer: only search for fuzz function in .go files

[kmoe]

Found this issue while updating HCL fuzzer to Go 1.18 native fuzzing.

Issue

Prior to this change, $fuzzer_filename is populated with a list of all files containing the fuzz $function string, whether they be git index file, README, Go file, or anything else.

These multiple files are passed to rewrite_go_fuzz_harness on line 86 as separate arguments:

+ rewrite_go_fuzz_harness /src/hcl/hclsyntax/fuzz/README.md /src/hcl/hclsyntax/fuzz/fuzz_test.go FuzzParseTemplate

This leads to an error on line 31 as the arguments to rewrite_go_fuzz_harness are now incorrect.

+ fuzzer_filename=/src/hcl/hclsyntax/fuzz/README.md
+ fuzz_function=/src/hcl/hclsyntax/fuzz/fuzz_test.go
[...]
+ fuzzer_fn=/src/hcl/hclsyntax/fuzz/README.md_fuzz_.go
+ echo 'replacing *testing.F'
replacing *testing.F
+ sed -i 's/func /src/hcl/hclsyntax/fuzz/fuzz_test.go(\([a-zA-Z0-9]*\) \*testing\.F)/func /src/hcl/hclsyntax/fuzz/fuzz_test.go(\1 \*go118fuzzbuildutils\.F)/g' /src/hcl/hclsyntax/fuzz/README.md_fuzz_.go
sed: -e expression #1, char 13: unknown option to `s'

Solution

Limiting the grep to .go files (a47f2e0) fixes the case in which the fuzz $function string is present in one Go file and one or more non-Go files.

Subsequent lines of the script will still break if $function is present in more than one Go file. ca6e880 suggests erroring out in this case.

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[AdamKorcz]

Thanks a lot for this. Is there any chance you could also get rid of the -r flag?

[kmoe]

Sure, is there any particular reason that was left as a TODO - anything to look out for here?

[AdamKorcz]

Sure, is there any particular reason that was left as a TODO - anything to look out for here?

Not really. There shouldn't be anything contextual in OSS-Fuzz that caused the -r flag to be in that line.

[Navidem]

@kmoe friendly ping :)

[kmoe]

The first commit was superseded by #8238, so I've rebased.

Also removed the redundant grep -r flags.

@AdamKorcz @Navidem, thanks for your patience. This is ready for review.

[jonathanmetzman]

/gcbrun trial_build.py go --engine libfuzzer --sanitizer coverage address

[jonathanmetzman]

Are we still interested in merging this?