[libc][stdlib] Simplify getenv_test by using strcmp instead of custom helper (#163055)

[libc][stdlib] Simplify getenv_test by using inline_strcmp instead of custom helper

Replace the custom `my_streq` helper function with LLVM libc's
`inline_strcmp` utility from `src/string/memory_utils/inline_strcmp.h`.

Changes:
- Remove 18-line custom `my_streq` implementation
- Use `inline_strcmp` with a simple comparator lambda for string comparisons
- Replace `my_streq(..., nullptr)` checks with direct `== nullptr` comparisons
- Maintain identical test coverage while reducing code duplication

Benefits:
- Uses existing, well-tested LLVM libc infrastructure
- Clearer test assertions with standard comparison functions
- More concise code (reduced from ~48 to ~33 lines)
- Consistent with LLVM libc coding practices

The test continues to verify:
- Empty string handling
- Invalid name handling ('=')
- Missing environment variable queries
- Correct retrieval of existing variables (FRANCE, GERMANY, PATH)
- Partial name matching behavior (FRANC vs FRANCE, FRANCE1 vs FRANCE)

Author: kaladron

libc/test/integration/src/stdlib/getenv_test.cpp

@@ -7,43 +7,28 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/stdlib/getenv.h"
+#include "src/string/memory_utils/inline_strcmp.h"
 
 #include "test/IntegrationTest/test.h"
 
-static bool my_streq(const char *lhs, const char *rhs) {
-  if (lhs == rhs)
-    return true;
-  if (((lhs == static_cast<char *>(nullptr)) &&
-       (rhs != static_cast<char *>(nullptr))) ||
-      ((lhs != static_cast<char *>(nullptr)) &&
-       (rhs == static_cast<char *>(nullptr)))) {
-    return false;
-  }
-  const char *l, *r;
-  for (l = lhs, r = rhs; *l != '\0' && *r != '\0'; ++l, ++r)
-    if (*l != *r)
-      return false;
-
-  return *l == '\0' && *r == '\0';
-}
-
 TEST_MAIN([[maybe_unused]] int argc, [[maybe_unused]] char **argv,
           [[maybe_unused]] char **envp) {
-  ASSERT_TRUE(
-      my_streq(LIBC_NAMESPACE::getenv(""), static_cast<char *>(nullptr)));
-  ASSERT_TRUE(
-      my_streq(LIBC_NAMESPACE::getenv("="), static_cast<char *>(nullptr)));
-  ASSERT_TRUE(my_streq(LIBC_NAMESPACE::getenv("MISSING ENV VARIABLE"),
-                       static_cast<char *>(nullptr)));
-  ASSERT_FALSE(
-      my_streq(LIBC_NAMESPACE::getenv("PATH"), static_cast<char *>(nullptr)));
-  ASSERT_TRUE(my_streq(LIBC_NAMESPACE::getenv("FRANCE"), "Paris"));
-  ASSERT_FALSE(my_streq(LIBC_NAMESPACE::getenv("FRANCE"), "Berlin"));
-  ASSERT_TRUE(my_streq(LIBC_NAMESPACE::getenv("GERMANY"), "Berlin"));
-  ASSERT_TRUE(
-      my_streq(LIBC_NAMESPACE::getenv("FRANC"), static_cast<char *>(nullptr)));
-  ASSERT_TRUE(my_streq(LIBC_NAMESPACE::getenv("FRANCE1"),
-                       static_cast<char *>(nullptr)));
+  auto comp = [](char l, char r) -> int { return l - r; };
+  ASSERT_TRUE(LIBC_NAMESPACE::getenv("") == nullptr);
+  ASSERT_TRUE(LIBC_NAMESPACE::getenv("=") == nullptr);
+  ASSERT_TRUE(LIBC_NAMESPACE::getenv("MISSING ENV VARIABLE") == nullptr);
+  ASSERT_FALSE(LIBC_NAMESPACE::getenv("PATH") == nullptr);
+  ASSERT_EQ(LIBC_NAMESPACE::inline_strcmp(LIBC_NAMESPACE::getenv("FRANCE"),
+                                          "Paris", comp),
+            0);
+  ASSERT_NE(LIBC_NAMESPACE::inline_strcmp(LIBC_NAMESPACE::getenv("FRANCE"),
+                                          "Berlin", comp),
+            0);
+  ASSERT_EQ(LIBC_NAMESPACE::inline_strcmp(LIBC_NAMESPACE::getenv("GERMANY"),
+                                          "Berlin", comp),
+            0);
+  ASSERT_TRUE(LIBC_NAMESPACE::getenv("FRANC") == nullptr);
+  ASSERT_TRUE(LIBC_NAMESPACE::getenv("FRANCE1") == nullptr);
 
   return 0;
 }