diff --git a/benchmarks/util.h b/benchmarks/util.h
index 99eed5f0a..347dc3571 100644
--- a/benchmarks/util.h
+++ b/benchmarks/util.h
@@ -71,7 +71,7 @@ char* GetAlignedPtrFilled(std::vector<char>* buf, size_t alignment, size_t nbyte
 
 bool LockToCPU(int cpu_to_lock);
 
-static __inline __attribute__ ((__always_inline__)) void MakeAllocationResident(
+static inline __attribute__((__always_inline__)) void MakeAllocationResident(
     void* ptr, size_t nbytes, int pagesize) {
   uint8_t* data = reinterpret_cast<uint8_t*>(ptr);
   for (size_t i = 0; i < nbytes; i += pagesize) {
diff --git a/libc/bionic/sys_statvfs.cpp b/libc/bionic/sys_statvfs.cpp
index b3a0aca0c..3a05c3fa6 100644
--- a/libc/bionic/sys_statvfs.cpp
+++ b/libc/bionic/sys_statvfs.cpp
@@ -17,7 +17,7 @@
 #include <sys/statfs.h>
 #include <sys/statvfs.h>
 
-static __inline void __bionic_statfs_to_statvfs(const struct statfs* src, struct statvfs* dst) {
+static inline void __bionic_statfs_to_statvfs(const struct statfs* src, struct statvfs* dst) {
   dst->f_bsize = src->f_bsize;
   dst->f_frsize = src->f_frsize;
   dst->f_blocks = src->f_blocks;
diff --git a/libc/include/bits/threads_inlines.h b/libc/include/bits/threads_inlines.h
index 5878e0acc..459866ed8 100644
--- a/libc/include/bits/threads_inlines.h
+++ b/libc/include/bits/threads_inlines.h
@@ -124,7 +124,7 @@ struct __bionic_thrd_data {
 };
 #pragma clang diagnostic pop
 
-static inline void* _Nonnull __bionic_thrd_trampoline(void* _Nonnull __arg) {
+static __inline void* _Nonnull __bionic_thrd_trampoline(void* _Nonnull __arg) {
   struct __bionic_thrd_data __data =
       *__BIONIC_CAST(static_cast, struct __bionic_thrd_data*, __arg);
   free(__arg);
diff --git a/libc/include/strings.h b/libc/include/strings.h
index 2f4f7641a..4b8cc08e3 100644
--- a/libc/include/strings.h
+++ b/libc/include/strings.h
@@ -61,13 +61,13 @@ __BEGIN_DECLS
 
 /** Deprecated. Use memmove() instead. */
 #define bcopy(b1, b2, len) __bionic_bcopy((b1), (b2), (len))
-static __inline__ __always_inline void __bionic_bcopy(const void* _Nonnull b1, void* _Nonnull b2, size_t len) {
+static __inline __always_inline void __bionic_bcopy(const void* _Nonnull b1, void* _Nonnull b2, size_t len) {
   __builtin_memmove(b2, b1, len);
 }
 
 /** Deprecated. Use memset() instead. */
 #define bzero(b, len) __bionic_bzero((b), (len))
-static __inline__ __always_inline void __bionic_bzero(void* _Nonnull b, size_t len) {
+static __inline __always_inline void __bionic_bzero(void* _Nonnull b, size_t len) {
   __builtin_memset(b, 0, len);
 }
 
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 7625d3886..5d1718e94 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -87,9 +87,12 @@
 #define	__STRING(x)	#x
 #define	___STRING(x)	__STRING(x)
 
-#if defined(__cplusplus)
-#define	__inline	inline		/* convert to C++ keyword */
-#endif /* !__cplusplus */
+// C++ has `inline` as a keyword, as does C99, but ANSI C (aka C89 aka C90)
+// does not. Everything accepts the `__inline__` extension though. We could
+// just use that directly in our own code, but there's historical precedent
+// for `__inline` meaning it's still used in upstream BSD code (and potentially
+// downstream in vendor or app code).
+#define	__inline __inline__
 
 #define __always_inline __attribute__((__always_inline__))
 #define __attribute_const__ __attribute__((__const__))
@@ -260,7 +263,7 @@
  * them available externally. FORTIFY'ed functions try to be as close to possible as 'invisible';
  * having stack protectors detracts from that (b/182948263).
  */
-#  define __BIONIC_FORTIFY_INLINE static __inline__ __attribute__((__no_stack_protector__)) \
+#  define __BIONIC_FORTIFY_INLINE static __inline __attribute__((__no_stack_protector__)) \
       __always_inline __VERSIONER_FORTIFY_INLINE
 /*
  * We should use __BIONIC_FORTIFY_VARIADIC instead of __BIONIC_FORTIFY_INLINE
@@ -268,9 +271,9 @@
  * The __always_inline attribute is useless, misleading, and could trigger
  * clang compiler bug to incorrectly inline variadic functions.
  */
-#  define __BIONIC_FORTIFY_VARIADIC static __inline__
+#  define __BIONIC_FORTIFY_VARIADIC static __inline
 /* Error functions don't have bodies, so they can just be static. */
-#  define __BIONIC_ERROR_FUNCTION_VISIBILITY static __attribute__((__unused__))
+#  define __BIONIC_ERROR_FUNCTION_VISIBILITY static __unused
 #else
 /* Further increase sharing for some inline functions */
 #  define __pass_object_size_n(n)