1483130 - fuzzed code not in clang coverage report

Status: RESOLVED WORKSFORME

(Core :: Fuzzing, defect)

Description

[u473386]

User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36

Steps to reproduce:

Compile with clang and set this (also for CXXFLAGS).

export CFLAGS = "-fprofile-instr-generate -fcoverage-mapping"

Make a fuzzing build, and run a target.

$ MOZ_RUN_GTEST=1 LIBFUZZER=1 FUZZER=SdpParser /path/to/firefox -runs=100

Make the report.

$ llvm-profdata merge -sparse default.profraw -o default.profdata
default.profraw: _ZNK7mozilla5MaybeIiEdeEv: Function basic block count change detected (counter mismatch)
Make sure that all profile data to be merged is generated from the same binary.
default.profraw: _ZN7mozilla5MaybeIiE7emplaceIJRiEEEvDpOT_: Function basic block count change detected (counter mismatch)
default.profraw: _ZNK7mozilla5MaybeIiE3refEv: Function basic block count change detected (counter mismatch)
default.profraw: _ZN7mozilla5MaybeIiE3refEv: Function basic block count change detected (counter mismatch)
default.profraw: _ZN7mozilla5MaybeIDiE7emplaceIJRDiEEEvDpOT_: Function basic block count change detected (counter mismatch)
default.profraw: _ZN7mozilla5MaybeIDiE3refEv: Function basic block count change detected (counter mismatch)

Print the report.

$ llvm-cov report /path/to/firefox -instr-profile=default.profdata > llvm-cov.txt
warning: 108 functions have mismatched data

https://gist.github.com/pdknsk/dfd00b041315b5362d871aed7295a843

The fuzzed code is missing.

It is counted correctly, so the problem must be those warning messages.

$ llvm-profdata show default.profdata --function=RunSdpParserFuzzing
Counters:
  sdp_parser_libfuzz.cpp:_ZL19RunSdpParserFuzzingPKhm:
    Hash: 0x0000000000000018
    Counters: 1
    Function count: 100
Instrumentation level: Front-end
Functions shown: 1
Total functions: 31162
Maximum function count: 12988953
Maximum internal block count: 32702464

Comment 1

[u473386]

Was missing an argument to llvm-cov.