Allow Fingerprint::fromString to fail, returning None on bad input.

Author: David Ungar

include/swift/Basic/Fingerprint.h

@@ -71,22 +71,12 @@ class Fingerprint final {
   explicit Fingerprint(Fingerprint::Core value) : core(value) {}
 
   /// Creates a fingerprint value from the given input string that is known to
-  /// be a 32-byte hash value.
+  /// be a 32-byte hash value, i.e. that represent a valid 32-bit hex integer.
   ///
-  /// In +asserts builds, strings that violate this invariant will crash. If a
-  /// fingerprint value is needed to represent an "invalid" state, use a
-  /// vocabulary type like \c Optional<Fingerprint> instead.
-  static Fingerprint fromString(llvm::StringRef value);
-
-  /// Creates a fingerprint value from the given input string literal.
-  template <std::size_t N>
-  explicit Fingerprint(const char (&literal)[N])
-    : Fingerprint{Fingerprint::fromString({literal, N-1}).core} {
-      static_assert(N == Fingerprint::DIGEST_LENGTH + 1,
-                    "String literal must be 32 bytes in length!");
-    }
-
-  /// Creates a fingerprint value by consuming the given \c MD5Result from LLVM.
+  /// Strings that violate this invariant will return a null optional.
+  static llvm::Optional<Fingerprint> fromString(llvm::StringRef value);
+
+ /// Creates a fingerprint value by consuming the given \c MD5Result from LLVM.
   explicit Fingerprint(llvm::MD5::MD5Result &&MD5Value)
       : core{MD5Value.words()} {}
 

lib/AST/FineGrainedDependencyFormat.cpp

@@ -231,8 +231,10 @@ bool Deserializer::readFineGrainedDependencyGraph(SourceFileDepGraph &g,
       // FINGERPRINT_NODE must follow a SOURCE_FILE_DEP_GRAPH_NODE.
       if (node == nullptr)
         llvm::report_fatal_error("Unexpected FINGERPRINT_NODE record");
-
-      node->setFingerprint(Fingerprint::fromString(BlobData));
+      if (auto fingerprint = Fingerprint::fromString(BlobData))
+        node->setFingerprint(fingerprint.getValue());
+      else
+        llvm::report_fatal_error("Unconvertable FINGERPRINT_NODE record");
       break;
     }
 

lib/Basic/Fingerprint.cpp

@@ -29,7 +29,7 @@ void swift::simple_display(llvm::raw_ostream &out, const Fingerprint &fp) {
   out << fp.getRawValue();
 }
 
-Fingerprint Fingerprint::fromString(StringRef value) {
+Optional<Fingerprint> Fingerprint::fromString(StringRef value) {
   assert(value.size() == Fingerprint::DIGEST_LENGTH &&
          "Only supports 32-byte hash values!");
   auto fp = Fingerprint::ZERO();
@@ -41,11 +41,10 @@ Fingerprint Fingerprint::fromString(StringRef value) {
     std::istringstream s(value.drop_front(Fingerprint::DIGEST_LENGTH/2).str());
     s >> std::hex >> fp.core.second;
   }
-  if (value != fp.getRawValue()) {
-    llvm::errs() << "Fingerprint conversion failed; perhaps '" << value << "' is not a hex number";
-    llvm::errs().flush();
-    exit(1);
-  }
+  // If the input string is not valid hex, the conversion above can fail.
+  if (value != fp.getRawValue())
+    return None;
+
   return fp;
 }
 

lib/Serialization/ModuleFileCoreTableInfo.h

@@ -602,7 +602,10 @@ class ModuleFileSharedCore::DeclFingerprintsTableInfo {
     using namespace llvm::support;
     auto str = llvm::StringRef{reinterpret_cast<const char *>(data),
                                Fingerprint::DIGEST_LENGTH};
-    return Fingerprint::fromString(str);
+    if (auto fp = Fingerprint::fromString(str))
+      return fp.getValue();
+    llvm::errs() << "Unconvertable fingerprint\n";
+    abort();
   }
 };
 

tools/swift-dependency-tool/swift-dependency-tool.cpp

@@ -69,7 +69,12 @@ template <> struct ScalarTraits<swift::Fingerprint> {
     os << fp.getRawValue();
   }
   static StringRef input(StringRef s, void *, swift::Fingerprint &fp) {
-    fp = swift::Fingerprint::fromString(s);
+    if (auto convertedFP = swift::Fingerprint::fromString(s))
+      fp = convertedFP.getValue();
+    else {
+      llvm::errs() << "Failed to convert fingerprint '" << s << "'\n";
+      exit(1);
+    }
     return StringRef();
   }
   static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }