diff --git a/libc/test/utils/tools/CMakeLists.txt b/libc/test/utils/tools/CMakeLists.txt
--- a/libc/test/utils/tools/CMakeLists.txt
+++ b/libc/test/utils/tools/CMakeLists.txt
@@ -1,4 +1,4 @@
-add_custom_target(libc-tool-util-tests)
+add_libc_testsuite(libc-tool-unittests)
 
 function(add_libc_tool_unittest target_name)
 
@@ -27,7 +27,7 @@
     COMMAND $<TARGET_FILE:${target_name}> 
             ${LIBC_TOOL_UNITTEST_ARGS}
   )
-  add_dependencies(libc-tool-util-tests ${target_name})
+  add_dependencies(libc-tool-unittests ${target_name})
 
   target_compile_options(${target_name} PUBLIC -fno-rtti)
   target_link_libraries(${target_name} PRIVATE LLVMSupport)
diff --git a/libc/test/utils/tools/WrapperGen/CMakeLists.txt b/libc/test/utils/tools/WrapperGen/CMakeLists.txt
--- a/libc/test/utils/tools/WrapperGen/CMakeLists.txt
+++ b/libc/test/utils/tools/WrapperGen/CMakeLists.txt
@@ -1,4 +1,5 @@
-add_libc_tool_unittest( wrappergen_test
+add_libc_tool_unittest(
+  wrappergen_test
   SRCS 
     wrappergen_test.cpp   
   ARGS
diff --git a/libc/test/utils/tools/WrapperGen/wrappergen_test.cpp b/libc/test/utils/tools/WrapperGen/wrappergen_test.cpp
--- a/libc/test/utils/tools/WrapperGen/wrappergen_test.cpp
+++ b/libc/test/utils/tools/WrapperGen/wrappergen_test.cpp
@@ -12,6 +12,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
+#include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/raw_ostream.h"
@@ -149,6 +150,49 @@
   // would break this test.
 }
 
+TEST_F(WrapperGenTest, DeclStrlenAliasUsingAliaseeFile) {
+  llvm::Optional<llvm::StringRef> Redirects[] = {
+      llvm::None, llvm::StringRef(STDOutFile.get().TmpName),
+      llvm::StringRef(STDErrFile.get().TmpName)};
+
+  const char *AliaseeFileContent = "abc\nxyz__llvm_libcSTRLEN_ALIAS\nijk\n";
+  llvm::SmallVector<char> AliaseeFilePath;
+  auto AliaseeFileCreateError = llvm::sys::fs::createUniqueFile(
+      "libc-wrappergen-test-aliasee-file-%%-%%-%%-%%.txt", AliaseeFilePath);
+  ASSERT_FALSE(AliaseeFileCreateError);
+  auto AliaseeFileWriteError = llvm::writeFileAtomically(
+      "libc-wrappergen-temp-test-aliasee-file-%%-%%-%%-%%.txt",
+      llvm::StringRef(AliaseeFilePath.data()),
+      llvm::StringRef(AliaseeFileContent));
+  ASSERT_FALSE(AliaseeFileWriteError);
+
+  llvm::StringRef ArgV[] = {ProgPath,
+                            llvm::StringRef(IncludeArg),
+                            llvm::StringRef(APIArg),
+                            "--aliasee-file",
+                            llvm::StringRef(AliaseeFilePath.data()),
+                            "--name",
+                            "strlen"};
+
+  int ExitCode =
+      llvm::sys::ExecuteAndWait(ProgPath, ArgV, llvm::None, Redirects);
+
+  EXPECT_EQ(ExitCode, 0);
+
+  auto STDErrOrError = llvm::MemoryBuffer::getFile(STDErrFile.get().TmpName);
+  std::string STDErrOutput = STDErrOrError.get()->getBuffer().str();
+
+  ASSERT_EQ(STDErrOutput, "");
+
+  auto STDOutOrError = llvm::MemoryBuffer::getFile(STDOutFile.get().TmpName);
+  std::string STDOutOutput = STDOutOrError.get()->getBuffer().str();
+
+  ASSERT_EQ(STDOutOutput,
+            "extern \"C\" size_t strlen(const char * __arg0) "
+            "__attribute__((alias(\"xyz__llvm_libcSTRLEN_ALIAS\")));\n");
+}
+
+/////////////////////////////////////////////////////////////////////
 /////////////////////////////////////////////////////////////////////
 // BAD INPUT TESTS
 // all of the tests after this point are testing inputs that should
@@ -245,3 +289,34 @@
 
   ASSERT_EQ(STDOutOutput, "");
 }
+
+TEST_F(WrapperGenTest, RunWithAliaseeFileMissingLLVMLibcName) {
+  llvm::Optional<llvm::StringRef> Redirects[] = {
+      llvm::None, llvm::StringRef(STDOutFile.get().TmpName),
+      llvm::StringRef(STDErrFile.get().TmpName)};
+
+  llvm::SmallVector<char> AliaseeFilePath;
+  auto AliaseeFileCreateError = llvm::sys::fs::createUniqueFile(
+      "libc-wrappergen-test-aliasee-file-%%-%%-%%-%%.txt", AliaseeFilePath);
+  ASSERT_FALSE(AliaseeFileCreateError);
+
+  llvm::StringRef ArgV[] = {ProgPath,
+                            llvm::StringRef(IncludeArg),
+                            llvm::StringRef(APIArg),
+                            "--aliasee-file",
+                            llvm::StringRef(AliaseeFilePath.data()),
+                            "--name",
+                            "strlen"};
+
+  int ExitCode =
+      llvm::sys::ExecuteAndWait(ProgPath, ArgV, llvm::None, Redirects);
+
+  EXPECT_NE(ExitCode, 0);
+
+  auto STDErrOrError = llvm::MemoryBuffer::getFile(STDErrFile.get().TmpName);
+  std::string STDErrOutput = STDErrOrError.get()->getBuffer().str();
+
+  ASSERT_EQ(STDErrOutput, ("error: Did not find an LLVM libc mangled name in " +
+                           AliaseeFilePath + "\n")
+                              .str());
+}
diff --git a/libc/utils/tools/WrapperGen/Main.cpp b/libc/utils/tools/WrapperGen/Main.cpp
--- a/libc/utils/tools/WrapperGen/Main.cpp
+++ b/libc/utils/tools/WrapperGen/Main.cpp
@@ -42,7 +42,16 @@
   auto ErrorOrBuf = llvm::MemoryBuffer::getFile(AliaseeFile);
   if (!ErrorOrBuf)
     llvm::PrintFatalError("Unable to read the aliasee file " + AliaseeFile);
-  return std::string(ErrorOrBuf.get()->getBuffer().trim());
+  llvm::StringRef FileContent = ErrorOrBuf.get()->getBuffer().trim();
+  llvm::SmallVector<llvm::StringRef> Lines;
+  FileContent.split(Lines, '\n');
+  for (llvm::StringRef L : Lines) {
+    if (L.contains("__llvm_libc"))
+      return std::string(L);
+  }
+  llvm::PrintFatalError("Did not find an LLVM libc mangled name in " +
+                        AliaseeFile);
+  return std::string();
 }
 
 static bool WrapperGenMain(llvm::raw_ostream &OS, llvm::RecordKeeper &Records) {