Build a String from a view by data(), not c_str()

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
     - name: Configure
       run: cmake -S . -B build-cmake -DCMAKE_BUILD_TYPE=${{ matrix.build_type }} -DEQ_BUILD_TESTS=ON
     - name: Build
-      run: cmake --build build-cmake --config ${{ matrix.build_type }} --parallel
+      run: cmake --build build-cmake --config ${{ matrix.build_type }} --parallel 4
     - name: Test
       run: ctest --test-dir build-cmake --build-config ${{ matrix.build_type }} --output-on-failure --no-tests=error
     - name: Setup tmate debug session

base/strings/base_string.h

@@ -316,11 +316,13 @@ class BasicBaseString {
     }
   }
 
+  // data(), not c_str(): a view (StringRef) has c_str() too, but a slice of a
+  // longer string is not null-terminated and its c_str() refuses in debug.
   template <class TOther>
     requires(base::HasStringTraits<TOther, value_type>)
   BasicBaseString(const TOther& other) {
     init_empty();
-    assign(other.c_str(), static_cast<size_type>(other.size()));
+    assign(other.data(), static_cast<size_type>(other.size()));
   }
 
   // From any non-owning character range (std::string_view, base::StringRef).

base/strings/base_string_test.cc

@@ -603,6 +603,15 @@ TEST(BaseStringSearch, ReverseFindHonoursThePosition) {
   EXPECT_EQ(s.rfind('.', 2), 1u);
 }
 
+TEST(BaseStringAssign, ConstructsFromAnUnterminatedSlice) {
+  // A slice of a longer string ends before the terminator; copying it must
+  // take (data, size), never c_str().
+  const base::StringRef whole("rxe://config/low.ini");
+  const base::String mount(whole.substr(0, 3));
+  EXPECT_EQ(mount, "rxe");
+  EXPECT_EQ(mount.size(), 3u);
+}
+
 TEST(BaseStringAssign, AssignsFromAnotherStringLike) {
   base::StringRef ref("hello");
   base::String s;