diff --git a/libc/arch-arm/generic/bionic/strlen.c b/libc/arch-arm/generic/bionic/strlen.c
index f6b9209..dccd564 100644
--- a/libc/arch-arm/generic/bionic/strlen.c
+++ b/libc/arch-arm/generic/bionic/strlen.c
@@ -67,53 +67,46 @@
         "sub     %[t], %[v], %[mask], lsr #7\n"
         "and     %[t], %[t], %[mask]        \n"
         "bics    %[t], %[t], %[v]           \n"
-        "it      eq                         \n"
-        "ldreq   %[v], [%[s]], #4           \n"
+        "bne     1f                         \n"
+        "ldr     %[v], [%[s]], #4           \n"
 #if !defined(__OPTIMIZE_SIZE__)
-        "bne     1f                         \n"
         "sub     %[t], %[v], %[mask], lsr #7\n"
         "and     %[t], %[t], %[mask]        \n"
         "bics    %[t], %[t], %[v]           \n"
-        "it      eq                         \n"
-        "ldreq   %[v], [%[s]], #4           \n"
         "bne     1f                         \n"
+        "ldr     %[v], [%[s]], #4           \n"
         "sub     %[t], %[v], %[mask], lsr #7\n"
         "and     %[t], %[t], %[mask]        \n"
         "bics    %[t], %[t], %[v]           \n"
-        "it      eq                         \n"
-        "ldreq   %[v], [%[s]], #4           \n"
         "bne     1f                         \n"
+        "ldr     %[v], [%[s]], #4           \n"
         "sub     %[t], %[v], %[mask], lsr #7\n"
         "and     %[t], %[t], %[mask]        \n"
         "bics    %[t], %[t], %[v]           \n"
-        "it      eq                         \n"
-        "ldreq   %[v], [%[s]], #4           \n"
         "bne     1f                         \n"
+        "ldr     %[v], [%[s]], #4           \n"
         "sub     %[t], %[v], %[mask], lsr #7\n"
         "and     %[t], %[t], %[mask]        \n"
         "bics    %[t], %[t], %[v]           \n"
-        "it      eq                         \n"
-        "ldreq   %[v], [%[s]], #4           \n"
         "bne     1f                         \n"
+        "ldr     %[v], [%[s]], #4           \n"
         "sub     %[t], %[v], %[mask], lsr #7\n"
         "and     %[t], %[t], %[mask]        \n"
         "bics    %[t], %[t], %[v]           \n"
-        "it      eq                         \n"
-        "ldreq   %[v], [%[s]], #4           \n"
         "bne     1f                         \n"
+        "ldr     %[v], [%[s]], #4           \n"
         "sub     %[t], %[v], %[mask], lsr #7\n"
         "and     %[t], %[t], %[mask]        \n"
         "bics    %[t], %[t], %[v]           \n"
-        "it      eq                         \n"
-        "ldreq   %[v], [%[s]], #4           \n"
         "bne     1f                         \n"
+        "ldr     %[v], [%[s]], #4           \n"
         "sub     %[t], %[v], %[mask], lsr #7\n"
         "and     %[t], %[t], %[mask]        \n"
         "bics    %[t], %[t], %[v]           \n"
-        "it      eq                         \n"
-        "ldreq   %[v], [%[s]], #4           \n"
+        "bne     1f                         \n"
+        "ldr     %[v], [%[s]], #4           \n"
 #endif
-        "beq     0b                         \n"
+        "b       0b                         \n"
         "1:                                 \n"
         "add     %[l], %[l], %[s]           \n"
         "tst     %[v], #0xFF                \n"
diff --git a/libc/bionic/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 9197aa3..9be86f1 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -278,7 +278,7 @@
       munmap(thread->attr.stack_base, thread->mmap_size);
     }
     async_safe_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s",
-                          strerror(errno));
+                          strerror(clone_errno));
     return clone_errno;
   }
 
diff --git a/libc/include/string.h b/libc/include/string.h
index 631b3dd..164146d 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -58,8 +58,11 @@
 char* __strchr_chk(const char*, int, size_t) __INTRODUCED_IN(18);
 #if defined(__USE_GNU)
 #if defined(__cplusplus)
+/* The versioner doesn't handle C++ blocks yet, so manually guarded. */
+#if __ANDROID_API__ >= 24
 extern "C++" char* strchrnul(char*, int) __RENAME(strchrnul) __attribute_pure__ __INTRODUCED_IN(24);
 extern "C++" const char* strchrnul(const char*, int) __RENAME(strchrnul) __attribute_pure__ __INTRODUCED_IN(24);
+#endif  /* __ANDROID_API__ >= 24 */
 #else
 char* strchrnul(const char*, int) __attribute_pure__ __INTRODUCED_IN(24);
 #endif
@@ -125,8 +128,11 @@
  * It doesn't modify its argument, and in C++ it's const-correct.
  */
 #if defined(__cplusplus)
+/* The versioner doesn't handle C++ blocks yet, so manually guarded. */
+#if __ANDROID_API__ >= 23
 extern "C++" char* basename(char*) __RENAME(__gnu_basename) __INTRODUCED_IN(23);
 extern "C++" const char* basename(const char*) __RENAME(__gnu_basename) __INTRODUCED_IN(23);
+#endif  /* __ANDROID_API__ >= 23 */
 #else
 char* basename(const char*) __RENAME(__gnu_basename) __INTRODUCED_IN(23);
 #endif
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 9541520..71d8426 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -239,7 +239,8 @@
 
 #define __BIONIC_FORTIFY_UNKNOWN_SIZE ((size_t) -1)
 
-#if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
+#if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && \
+      (defined(__clang__) || (defined(__OPTIMIZE__) && __OPTIMIZE__ > 0))
 #  define __BIONIC_FORTIFY 1
 #  if _FORTIFY_SOURCE == 2
 #    define __bos_level 1
@@ -281,8 +282,7 @@
 #define __pass_object_size __pass_object_size_n(__bos_level)
 #define __pass_object_size0 __pass_object_size_n(0)
 
-/* FIXME: This should be __BIONIC_FORTIFY, but we don't enable FORTIFY in -O0. */
-#if (defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0) || defined(__BIONIC_DECLARE_FORTIFY_HELPERS)
+#if defined(__BIONIC_FORTIFY) || defined(__BIONIC_DECLARE_FORTIFY_HELPERS)
 #  define __BIONIC_INCLUDE_FORTIFY_HEADERS 1
 #endif
 
diff --git a/libc/private/CFIShadow.h b/libc/private/CFIShadow.h
index 26351db..1423d86 100644
--- a/libc/private/CFIShadow.h
+++ b/libc/private/CFIShadow.h
@@ -61,10 +61,8 @@
   // Alignment of __cfi_check.
   static constexpr uintptr_t kCfiCheckAlign = 1UL << kCfiCheckGranularity;  // 4K
 
-#if defined(__aarch64__)
-  static constexpr uintptr_t kMaxTargetAddr = 0x7fffffffff;
-#elif defined (__LP64__)
-  static constexpr uintptr_t kMaxTargetAddr = 0x7fffffffffff;
+#if defined (__LP64__)
+  static constexpr uintptr_t kMaxTargetAddr = 0xffffffffffff;
 #else
   static constexpr uintptr_t kMaxTargetAddr = 0xffffffff;
 #endif
diff --git a/libdl/libdl.arm.map b/libdl/libdl.arm.map
index 292bd97..9fc9d23 100644
--- a/libdl/libdl.arm.map
+++ b/libdl/libdl.arm.map
@@ -36,6 +36,7 @@
 
 LIBC_OMR1 { # future
   global:
+    __cfi_shadow_size; # future
     __cfi_slowpath; # future
     __cfi_slowpath_diag; # future
 } LIBC_N;
diff --git a/libdl/libdl.arm64.map b/libdl/libdl.arm64.map
index 2fe2c7b..bde6cab 100644
--- a/libdl/libdl.arm64.map
+++ b/libdl/libdl.arm64.map
@@ -35,6 +35,7 @@
 
 LIBC_OMR1 { # future
   global:
+    __cfi_shadow_size; # future
     __cfi_slowpath; # future
     __cfi_slowpath_diag; # future
 } LIBC_N;
diff --git a/libdl/libdl.map.txt b/libdl/libdl.map.txt
index 408d4dc..d1f4ab8 100644
--- a/libdl/libdl.map.txt
+++ b/libdl/libdl.map.txt
@@ -35,6 +35,7 @@
 
 LIBC_OMR1 { # future
   global:
+    __cfi_shadow_size; # future
     __cfi_slowpath; # future
     __cfi_slowpath_diag; # future
 } LIBC_N;
diff --git a/libdl/libdl.mips.map b/libdl/libdl.mips.map
index 2fe2c7b..bde6cab 100644
--- a/libdl/libdl.mips.map
+++ b/libdl/libdl.mips.map
@@ -35,6 +35,7 @@
 
 LIBC_OMR1 { # future
   global:
+    __cfi_shadow_size; # future
     __cfi_slowpath; # future
     __cfi_slowpath_diag; # future
 } LIBC_N;
diff --git a/libdl/libdl.mips64.map b/libdl/libdl.mips64.map
index 2fe2c7b..bde6cab 100644
--- a/libdl/libdl.mips64.map
+++ b/libdl/libdl.mips64.map
@@ -35,6 +35,7 @@
 
 LIBC_OMR1 { # future
   global:
+    __cfi_shadow_size; # future
     __cfi_slowpath; # future
     __cfi_slowpath_diag; # future
 } LIBC_N;
diff --git a/libdl/libdl.x86.map b/libdl/libdl.x86.map
index 2fe2c7b..bde6cab 100644
--- a/libdl/libdl.x86.map
+++ b/libdl/libdl.x86.map
@@ -35,6 +35,7 @@
 
 LIBC_OMR1 { # future
   global:
+    __cfi_shadow_size; # future
     __cfi_slowpath; # future
     __cfi_slowpath_diag; # future
 } LIBC_N;
diff --git a/libdl/libdl.x86_64.map b/libdl/libdl.x86_64.map
index 2fe2c7b..bde6cab 100644
--- a/libdl/libdl.x86_64.map
+++ b/libdl/libdl.x86_64.map
@@ -35,6 +35,7 @@
 
 LIBC_OMR1 { # future
   global:
+    __cfi_shadow_size; # future
     __cfi_slowpath; # future
     __cfi_slowpath_diag; # future
 } LIBC_N;
diff --git a/libdl/libdl_cfi.cpp b/libdl/libdl_cfi.cpp
index 8458564..483364f 100644
--- a/libdl/libdl_cfi.cpp
+++ b/libdl/libdl_cfi.cpp
@@ -38,6 +38,11 @@
   return &shadow_base_storage.v;
 }
 
+// Returns the size of the CFI shadow mapping, or 0 if CFI is not (yet) used in this process.
+extern "C" size_t __cfi_shadow_size() {
+  return shadow_base_storage.v != 0 ? CFIShadow::kShadowSize : 0;
+}
+
 static uint16_t shadow_load(void* p) {
   uintptr_t addr = reinterpret_cast<uintptr_t>(p);
   uintptr_t ofs = CFIShadow::MemToShadowOffset(addr);
diff --git a/linker/linker.cpp b/linker/linker.cpp
index a212624..8aadd14 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -3506,6 +3506,9 @@
   g_default_namespace.set_permitted_paths(default_ns_config->permitted_paths());
 
   namespaces[default_ns_config->name()] = &g_default_namespace;
+  if (default_ns_config->visible()) {
+    g_exported_namespaces[default_ns_config->name()] = &g_default_namespace;
+  }
 
   // 2. Initialize other namespaces
 
diff --git a/tests/cfi_test.cpp b/tests/cfi_test.cpp
index 5e627a7..088dda6 100644
--- a/tests/cfi_test.cpp
+++ b/tests/cfi_test.cpp
@@ -26,6 +26,7 @@
 extern "C" {
 void __cfi_slowpath(uint64_t CallSiteTypeId, void* Ptr);
 void __cfi_slowpath_diag(uint64_t CallSiteTypeId, void* Ptr, void* DiagData);
+size_t __cfi_shadow_size();
 }
 
 static void f() {}
@@ -36,6 +37,8 @@
   handle = dlopen("libcfi-test.so", RTLD_NOW | RTLD_LOCAL);
   ASSERT_TRUE(handle != nullptr) << dlerror();
 
+  EXPECT_NE(0U, __cfi_shadow_size());
+
 #define SYM(type, name) auto name = reinterpret_cast<type>(dlsym(handle, #name))
   SYM(int (*)(), get_count);
   SYM(uint64_t(*)(), get_last_type_id);
diff --git a/tools/versioner/src/Driver.cpp b/tools/versioner/src/Driver.cpp
index a094818..8a8e00a 100644
--- a/tools/versioner/src/Driver.cpp
+++ b/tools/versioner/src/Driver.cpp
@@ -119,7 +119,14 @@
 
   cmd.push_back("-DANDROID");
   cmd.push_back("-D__ANDROID_API__="s + std::to_string(type.api_level));
+  // FIXME: Re-enable FORTIFY properly once our clang in external/ is new enough
+  // to support diagnose_if without giving us syntax errors.
+#if 0
   cmd.push_back("-D_FORTIFY_SOURCE=2");
+#else
+  cmd.push_back("-D_FORTIFY_SOURCE=0");
+  cmd.push_back("-D__BIONIC_DECLARE_FORTIFY_HELPERS");
+#endif
   cmd.push_back("-D_GNU_SOURCE");
   cmd.push_back("-D_FILE_OFFSET_BITS="s + std::to_string(type.file_offset_bits));