diff --git a/src/string_view.c b/src/string_view.c
index 554294fa..bf6d7415 100644
--- a/src/string_view.c
+++ b/src/string_view.c
@@ -16,6 +16,7 @@
 
 #include <assert.h>
 #include <ctype.h>
+#include <limits.h>
 
 #include "copy.inl"
 #include "equals.inl"
@@ -101,9 +102,11 @@ char CpuFeatures_StringView_Back(const StringView view) {
 }
 
 StringView CpuFeatures_StringView_TrimWhitespace(StringView view) {
-  while (view.size && isspace(CpuFeatures_StringView_Front(view)))
+  while (view.size &&
+         isspace((unsigned char)CpuFeatures_StringView_Front(view)))
     view = CpuFeatures_StringView_PopFront(view, 1);
-  while (view.size && isspace(CpuFeatures_StringView_Back(view)))
+  while (view.size &&
+         isspace((unsigned char)CpuFeatures_StringView_Back(view)))
     view = CpuFeatures_StringView_PopBack(view, 1);
   return view;
 }
@@ -115,14 +118,16 @@ static int HexValue(const char c) {
   return -1;
 }
 
-// Returns -1 if view contains non digits.
+// Returns -1 if view contains non digits, is empty, or overflows.
 static int ParsePositiveNumberWithBase(const StringView view, int base) {
+  if (view.size == 0) return -1;
   int result = 0;
   StringView remainder = view;
   for (; remainder.size;
        remainder = CpuFeatures_StringView_PopFront(remainder, 1)) {
     const int value = HexValue(CpuFeatures_StringView_Front(remainder));
     if (value < 0 || value >= base) return -1;
+    if (result > (INT_MAX - value) / base) return -1;
     result = (result * base) + value;
   }
   return result;
diff --git a/test/string_view_test.cc b/test/string_view_test.cc
index 3af70c70..4e33de1f 100644
--- a/test/string_view_test.cc
+++ b/test/string_view_test.cc
@@ -124,19 +124,37 @@ TEST(StringViewTest, CpuFeatures_StringView_TrimWhitespace) {
             str("first middle last"));
   EXPECT_EQ(CpuFeatures_StringView_TrimWhitespace(str("first middle last")),
             str("first middle last"));
+  EXPECT_EQ(CpuFeatures_StringView_TrimWhitespace(str("")), str(""));
+  EXPECT_EQ(CpuFeatures_StringView_TrimWhitespace(str("   ")), str(""));
+  // Ensure non-ASCII characters (with high bit set) do not cause undefined behavior in isspace().
+  EXPECT_EQ(CpuFeatures_StringView_TrimWhitespace(str(" \xff abc \x80 ")),
+            str("\xff abc \x80"));
 }
 
 TEST(StringViewTest, CpuFeatures_StringView_ParsePositiveNumber) {
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("42")), 42);
+  EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0")), 0);
+  EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0x0")), 0);
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0x2a")), 42);
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0x2A")), 42);
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0x2A2a")), 10794);
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0x2a2A")), 10794);
 
+  EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0x")), -1);
+  EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0x ")), -1);
+  EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("0xG")), -1);
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("-10")), -1);
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("-0x2A")), -1);
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("abc")), -1);
   EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(str("")), -1);
+
+  // Overflow handling
+  EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(
+                str("999999999999999999999999999999")),
+            -1);
+  EXPECT_EQ(CpuFeatures_StringView_ParsePositiveNumber(
+                str("0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF")),
+            -1);
 }
 
 TEST(StringViewTest, CpuFeatures_StringView_CopyString) {