string_view: fix HasWord false negative after a non-boundary partial match

src/string_view.c

@@ -162,10 +162,15 @@ bool CpuFeatures_StringView_HasWord(const StringView line,
     if (index_of_word < 0) {
       return false;
     } else {
+      // index_of_word is relative to `remainder`; convert it to an absolute
+      // index into `line` so the boundary checks see the real neighbours.
+      // (On later iterations `remainder` no longer starts at `line`.)
+      const size_t absolute_index =
+          (line.size - remainder.size) + (size_t)index_of_word;
       const StringView before =
-          CpuFeatures_StringView_KeepFront(line, index_of_word);
+          CpuFeatures_StringView_KeepFront(line, absolute_index);
       const StringView after =
-          CpuFeatures_StringView_PopFront(line, index_of_word + word.size);
+          CpuFeatures_StringView_PopFront(line, absolute_index + word.size);
       const bool valid_before =
           before.size == 0 || CpuFeatures_StringView_Back(before) == separator;
       const bool valid_after =

test/string_view_test.cc

@@ -182,6 +182,14 @@ TEST(StringViewTest, CpuFeatures_StringView_HasWord) {
       CpuFeatures_StringView_HasWord(str("first middle last"), "mid", ' '));
   EXPECT_FALSE(
       CpuFeatures_StringView_HasWord(str("first middle last"), "las", ' '));
+  // Regression: the searched word appears as a real token, but an earlier
+  // non-boundary partial occurrence forces a second loop iteration. HasWord
+  // used to run the separator checks with a remainder-relative index against
+  // the whole line, producing a false negative on the real token.
+  EXPECT_TRUE(CpuFeatures_StringView_HasWord(str("foox foo"), "foo", ' '));
+  EXPECT_TRUE(CpuFeatures_StringView_HasWord(str("xvme vme"), "vme", ' '));
+  // A repeated prefix that is never its own token must still not match.
+  EXPECT_FALSE(CpuFeatures_StringView_HasWord(str("foofoo bar"), "foo", ' '));
 }
 
 TEST(StringViewTest, CpuFeatures_StringView_GetAttributeKeyValue) {