fuzz: add logging support to the fuzzer

This makes it a little easier to introspect what the regex crate is
doing. Just pass RUST_LOG=debug to get a general sense of things, and
RUST_LOG=trace to get a lot more output.

Author: BurntSushi

fuzz/Cargo.toml

@@ -16,11 +16,18 @@ cargo-fuzz = true
 [dependencies]
 arbitrary = { version = "1.3.0", features = ["derive"] }
 libfuzzer-sys = { version = "0.4.1", features = ["arbitrary-derive"] }
-regex = { path = ".." }
-regex-automata = { path = "../regex-automata" }
+regex = { path = "..", features = ["logging"] }
+regex-automata = { path = "../regex-automata", features = ["logging"] }
 regex-lite = { path = "../regex-lite" }
 regex-syntax = { path = "../regex-syntax", features = ["arbitrary"] }
 
+[dependencies.env_logger]
+# Note that this is currently using an older version because of the dependency
+# tree explosion that happened in 0.10.
+version = "0.9.3"
+default-features = false
+features = ["atty", "humantime", "termcolor"]
+
 # Prevent this from interfering with workspaces
 [workspace]
 members = ["."]

fuzz/fuzz_targets/ast_fuzz_match.rs

@@ -20,6 +20,8 @@ impl std::fmt::Debug for FuzzData {
 }
 
 fuzz_target!(|data: FuzzData| {
+    let _ = env_logger::try_init();
+
     let pattern = format!("{}", data.ast);
     let Ok(re) = RegexBuilder::new(&pattern).size_limit(1<<20).build() else {
         return

fuzz/fuzz_targets/ast_fuzz_match_bytes.rs

@@ -21,6 +21,8 @@ impl std::fmt::Debug for FuzzData {
 }
 
 fuzz_target!(|data: FuzzData| {
+    let _ = env_logger::try_init();
+
     let pattern = format!("{}", data.ast);
     let Ok(re) = RegexBuilder::new(&pattern).size_limit(1<<20).build() else {
         return

fuzz/fuzz_targets/ast_fuzz_regex.rs

@@ -18,6 +18,8 @@ impl std::fmt::Debug for FuzzData {
 }
 
 fuzz_target!(|data: FuzzData| {
+    let _ = env_logger::try_init();
+
     let pattern = format!("{}", data.ast);
     RegexBuilder::new(&pattern).size_limit(1 << 20).build().ok();
 });

fuzz/fuzz_targets/ast_roundtrip.rs

@@ -47,6 +47,8 @@ impl Visitor for VerboseVisitor {
 }
 
 fuzz_target!(|data: FuzzData| -> Corpus {
+    let _ = env_logger::try_init();
+
     let pattern = format!("{}", data.ast);
     let Ok(ast) = Parser::new().parse(&pattern) else {
         return Corpus::Keep;

fuzz/fuzz_targets/fuzz_regex_automata_deserialize_dense_dfa.rs

@@ -9,6 +9,8 @@ fuzz_target!(|data: &[u8]| {
 fn run(given_data: &[u8]) -> Option<()> {
     use regex_automata::dfa::Automaton;
 
+    let _ = env_logger::try_init();
+
     if given_data.len() < 2 {
         return None;
     }

fuzz/fuzz_targets/fuzz_regex_automata_deserialize_sparse_dfa.rs

@@ -9,6 +9,8 @@ fuzz_target!(|data: &[u8]| {
 fn run(given_data: &[u8]) -> Option<()> {
     use regex_automata::dfa::Automaton;
 
+    let _ = env_logger::try_init();
+
     if given_data.len() < 2 {
         return None;
     }

fuzz/fuzz_targets/fuzz_regex_lite_match.rs

@@ -48,6 +48,8 @@ re.is_match({haystack:?});
 }
 
 fuzz_target!(|case: FuzzCase| {
+    let _ = env_logger::try_init();
+
     let Ok(re) = regex_lite::RegexBuilder::new(case.pattern)
         .case_insensitive(case.case_insensitive)
         .multi_line(case.multi_line)

fuzz/fuzz_targets/fuzz_regex_match.rs

@@ -51,6 +51,8 @@ re.is_match({haystack:?});
 }
 
 fuzz_target!(|case: FuzzCase| {
+    let _ = env_logger::try_init();
+
     let Ok(re) = regex::RegexBuilder::new(case.pattern)
         .case_insensitive(case.case_insensitive)
         .multi_line(case.multi_line)