diff --git a/benchmarks/util.h b/benchmarks/util.h
index 3225bc2..d9e10f4 100644
--- a/benchmarks/util.h
+++ b/benchmarks/util.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef _BIONIC_BENCHMARKS_UTIL_H_
-#define _BIONIC_BENCHMARKS_UTIL_H_
+#pragma once
 
 #include <map>
 #include <mutex>
@@ -62,5 +61,3 @@
 char* GetAlignedPtrFilled(std::vector<char>* buf, size_t alignment, size_t nbytes, char fill_byte);
 
 bool LockToCPU(long cpu_to_lock);
-
-#endif // _BIONIC_BENCHMARKS_UTIL_H
diff --git a/libc/async_safe/include/async_safe/log.h b/libc/async_safe/include/async_safe/log.h
index 10833e4..415b48e 100644
--- a/libc/async_safe/include/async_safe/log.h
+++ b/libc/async_safe/include/async_safe/log.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _ASYNC_SAFE_LOG_LOG_H
-#define _ASYNC_SAFE_LOG_LOG_H
+#pragma once
 
 #include <sys/cdefs.h>
 #include <stdarg.h>
@@ -104,5 +103,3 @@
   } while(0)
 
 __END_DECLS
-
-#endif
diff --git a/libc/bionic/bionic_netlink.h b/libc/bionic/bionic_netlink.h
index bc0e3f0..a21200e 100644
--- a/libc/bionic/bionic_netlink.h
+++ b/libc/bionic/bionic_netlink.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef BIONIC_NETLINK_H
-#define BIONIC_NETLINK_H
+#pragma once
 
 #include <sys/types.h>
 
@@ -49,5 +48,3 @@
   char* data_;
   size_t size_;
 };
-
-#endif
diff --git a/libc/bionic/grp_pwd_file.h b/libc/bionic/grp_pwd_file.h
index ae8cd98..93dd852 100644
--- a/libc/bionic/grp_pwd_file.h
+++ b/libc/bionic/grp_pwd_file.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef GRP_PWD_FILE_H
-#define GRP_PWD_FILE_H
+#pragma once
 
 #include <grp.h>
 #include <pwd.h>
@@ -93,5 +92,3 @@
  private:
   MmapFile mmap_file_;
 };
-
-#endif
diff --git a/libc/bionic/jemalloc.h b/libc/bionic/jemalloc.h
index f7e8770..79a4f72 100644
--- a/libc/bionic/jemalloc.h
+++ b/libc/bionic/jemalloc.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef LIBC_BIONIC_JEMALLOC_H_
-#define LIBC_BIONIC_JEMALLOC_H_
+#pragma once
 
 #include <jemalloc/jemalloc.h>
 #include <malloc.h>  // For struct mallinfo.
@@ -35,5 +34,3 @@
 void* je_pvalloc(size_t);
 
 __END_DECLS
-
-#endif  // LIBC_BIONIC_DLMALLOC_H_
diff --git a/libc/bionic/libc_init_common.h b/libc/bionic/libc_init_common.h
index 5066652..6ce4d10 100644
--- a/libc/bionic/libc_init_common.h
+++ b/libc/bionic/libc_init_common.h
@@ -25,8 +25,8 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#ifndef LIBC_INIT_COMMON_H
-#define LIBC_INIT_COMMON_H
+
+#pragma once
 
 #include <sys/cdefs.h>
 
@@ -59,5 +59,3 @@
 __LIBC_HIDDEN__ void __libc_init_AT_SECURE(KernelArgumentBlock& args);
 
 #endif
-
-#endif
diff --git a/libc/bionic/malloc_info.h b/libc/bionic/malloc_info.h
index 5fffae9..257fec1 100644
--- a/libc/bionic/malloc_info.h
+++ b/libc/bionic/malloc_info.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef LIBC_BIONIC_MALLOC_INFO_H_
-#define LIBC_BIONIC_MALLOC_INFO_H_
+#pragma once
 
 #include <malloc.h>
 #include <sys/cdefs.h>
@@ -28,5 +27,3 @@
 __LIBC_HIDDEN__ struct mallinfo __mallinfo_bin_info(size_t, size_t);
 
 __END_DECLS
-
-#endif // LIBC_BIONIC_MALLOC_INFO_H_
diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index a4cba87..18f5aee 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -25,8 +25,8 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#ifndef _PTHREAD_INTERNAL_H_
-#define _PTHREAD_INTERNAL_H_
+
+#pragma once
 
 #include <pthread.h>
 #include <stdatomic.h>
@@ -172,5 +172,3 @@
 __LIBC_HIDDEN__ extern void __bionic_atfork_run_prepare();
 __LIBC_HIDDEN__ extern void __bionic_atfork_run_child();
 __LIBC_HIDDEN__ extern void __bionic_atfork_run_parent();
-
-#endif /* _PTHREAD_INTERNAL_H_ */
diff --git a/libc/malloc_debug/BacktraceData.h b/libc/malloc_debug/BacktraceData.h
index c8234dc..3c15348 100644
--- a/libc/malloc_debug/BacktraceData.h
+++ b/libc/malloc_debug/BacktraceData.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef DEBUG_MALLOC_BACKTRACEDATA_H
-#define DEBUG_MALLOC_BACKTRACEDATA_H
+#pragma once
 
 #include <stdint.h>
 
@@ -67,5 +66,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(BacktraceData);
 };
-
-#endif // DEBUG_MALLOC_BACKTRACEDATA_H
diff --git a/libc/malloc_debug/Config.h b/libc/malloc_debug/Config.h
index 349ad77..a310e09 100644
--- a/libc/malloc_debug/Config.h
+++ b/libc/malloc_debug/Config.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef MALLOC_DEBUG_CONFIG_H
-#define MALLOC_DEBUG_CONFIG_H
+#pragma once
 
 #include <stdint.h>
 
@@ -159,5 +158,3 @@
   uint8_t front_guard_value_;
   uint8_t rear_guard_value_;
 };
-
-#endif  // MALLOC_DEBUG_CONFIG_H
diff --git a/libc/malloc_debug/DebugData.h b/libc/malloc_debug/DebugData.h
index 7228a72..9aece0b 100644
--- a/libc/malloc_debug/DebugData.h
+++ b/libc/malloc_debug/DebugData.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef DEBUG_MALLOC_DEBUGDATA_H
-#define DEBUG_MALLOC_DEBUGDATA_H
+#pragma once
 
 #include <stdint.h>
 
@@ -106,5 +105,3 @@
 };
 
 extern DebugData* g_debug;
-
-#endif // MALLOC_DEBUG_DEBUGDATA_H
diff --git a/libc/malloc_debug/FreeTrackData.h b/libc/malloc_debug/FreeTrackData.h
index 0e8c177..bd3497d 100644
--- a/libc/malloc_debug/FreeTrackData.h
+++ b/libc/malloc_debug/FreeTrackData.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef DEBUG_MALLOC_FREETRACKDATA_H
-#define DEBUG_MALLOC_FREETRACKDATA_H
+#pragma once
 
 #include <stdint.h>
 #include <pthread.h>
@@ -75,5 +74,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(FreeTrackData);
 };
-
-#endif // DEBUG_MALLOC_FREETRACKDATA_H
diff --git a/libc/malloc_debug/GuardData.h b/libc/malloc_debug/GuardData.h
index ddf6ce1..7b21671 100644
--- a/libc/malloc_debug/GuardData.h
+++ b/libc/malloc_debug/GuardData.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef DEBUG_MALLOC_GUARDDATA_H
-#define DEBUG_MALLOC_GUARDDATA_H
+#pragma once
 
 #include <stdint.h>
 #include <string.h>
@@ -93,5 +92,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(RearGuardData);
 };
-
-#endif // DEBUG_MALLOC_GUARDDATA_H
diff --git a/libc/malloc_debug/MapData.h b/libc/malloc_debug/MapData.h
index 895f78f..a71f96d 100644
--- a/libc/malloc_debug/MapData.h
+++ b/libc/malloc_debug/MapData.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef DEBUG_MALLOC_MAPDATA_H
-#define DEBUG_MALLOC_MAPDATA_H
+#pragma once
 
 #include <sys/cdefs.h>
 
@@ -74,5 +73,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(MapData);
 };
-
-#endif  // DEBUG_MALLOC_MAPDATA_H
diff --git a/libc/malloc_debug/OptionData.h b/libc/malloc_debug/OptionData.h
index 5c2d272..3fa8e14 100644
--- a/libc/malloc_debug/OptionData.h
+++ b/libc/malloc_debug/OptionData.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef DEBUG_MALLOC_OPTIONDATA_H
-#define DEBUG_MALLOC_OPTIONDATA_H
+#pragma once
 
 // Forward Declarations
 class DebugData;
@@ -42,5 +41,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(OptionData);
 };
-
-#endif // MALLOC_DEBUG_OPTIONDATA_H
diff --git a/libc/malloc_debug/RecordData.h b/libc/malloc_debug/RecordData.h
index 97ad813..021a299 100644
--- a/libc/malloc_debug/RecordData.h
+++ b/libc/malloc_debug/RecordData.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef DEBUG_MALLOC_RECORDDATA_H
-#define DEBUG_MALLOC_RECORDDATA_H
+#pragma once
 
 #include <stdint.h>
 #include <pthread.h>
@@ -173,5 +172,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(RecordData);
 };
-
-#endif // DEBUG_MALLOC_RECORDDATA_H
diff --git a/libc/malloc_debug/TrackData.h b/libc/malloc_debug/TrackData.h
index 9a649b9..7201c49 100644
--- a/libc/malloc_debug/TrackData.h
+++ b/libc/malloc_debug/TrackData.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef DEBUG_MALLOC_TRACKDATA_H
-#define DEBUG_MALLOC_TRACKDATA_H
+#pragma once
 
 #include <stdint.h>
 #include <pthread.h>
@@ -75,5 +74,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(TrackData);
 };
-
-#endif // DEBUG_MALLOC_TRACKDATA_H
diff --git a/libc/malloc_debug/backtrace.h b/libc/malloc_debug/backtrace.h
index f570873..92ea237 100644
--- a/libc/malloc_debug/backtrace.h
+++ b/libc/malloc_debug/backtrace.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef MALLOC_DEBUG_BACKTRACE_H
-#define MALLOC_DEBUG_BACKTRACE_H
+#pragma once
 
 #include <stdint.h>
 #include <sys/cdefs.h>
@@ -39,5 +38,3 @@
 size_t backtrace_get(uintptr_t* frames, size_t frame_count);
 void backtrace_log(const uintptr_t* frames, size_t frame_count);
 std::string backtrace_string(const uintptr_t* frames, size_t frame_count);
-
-#endif // MALLOC_DEBUG_BACKTRACE_H
diff --git a/libc/malloc_debug/debug_disable.h b/libc/malloc_debug/debug_disable.h
index 9edb4df..0049595 100644
--- a/libc/malloc_debug/debug_disable.h
+++ b/libc/malloc_debug/debug_disable.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef MALLOC_DEBUG_DISABLE_H
-#define MALLOC_DEBUG_DISABLE_H
+#pragma once
 
 #include <sys/cdefs.h>
 
@@ -60,5 +59,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(ScopedDisableDebugCalls);
 };
-
-#endif  // MALLOC_DEBUG_DISABLE_H
diff --git a/libc/malloc_debug/debug_log.h b/libc/malloc_debug/debug_log.h
index ed4b541..54dd221 100644
--- a/libc/malloc_debug/debug_log.h
+++ b/libc/malloc_debug/debug_log.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef MALLOC_DEBUG_LOG_H
-#define MALLOC_DEBUG_LOG_H
+#pragma once
 
 #include <async_safe/log.h>
 
@@ -42,5 +41,3 @@
     async_safe_write_log(ANDROID_LOG_ERROR, "malloc_debug", (str))
 #define info_log(format, ...)  \
     async_safe_format_log(ANDROID_LOG_INFO, "malloc_debug", (format), ##__VA_ARGS__ )
-
-#endif  // MALLOC_DEBUG_LOG_H
diff --git a/libc/malloc_debug/malloc_debug.h b/libc/malloc_debug/malloc_debug.h
index 4a1e8da..18a6c2c 100644
--- a/libc/malloc_debug/malloc_debug.h
+++ b/libc/malloc_debug/malloc_debug.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef MALLOC_DEBUG_H
-#define MALLOC_DEBUG_H
+#pragma once
 
 #include <stdint.h>
 
@@ -70,5 +69,3 @@
 constexpr size_t FREE_TRACK_MEM_BUFFER_SIZE = 4096;
 
 extern const MallocDispatch* g_dispatch;
-
-#endif // MALLOC_DEBUG_H
diff --git a/libc/seccomp/include/seccomp_policy.h b/libc/seccomp/include/seccomp_policy.h
index add17b9..49280f4 100644
--- a/libc/seccomp/include/seccomp_policy.h
+++ b/libc/seccomp/include/seccomp_policy.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef SECCOMP_POLICY_H
-#define SECCOMP_POLICY_H
+#pragma once
 
 #include <stddef.h>
 #include <linux/filter.h>
@@ -23,5 +22,3 @@
 bool set_app_seccomp_filter();
 bool set_system_seccomp_filter();
 bool set_global_seccomp_filter();
-
-#endif
diff --git a/libc/seccomp/seccomp_bpfs.h b/libc/seccomp/seccomp_bpfs.h
index 8728c36..797dfc5 100644
--- a/libc/seccomp/seccomp_bpfs.h
+++ b/libc/seccomp/seccomp_bpfs.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef SECCOMP_BPFS_H
-#define SECCOMP_BPFS_H
+#pragma once
 
 #include <stddef.h>
 #include <linux/seccomp.h>
@@ -61,5 +60,3 @@
 extern const size_t mips64_system_filter_size;
 extern const struct sock_filter mips64_global_filter[];
 extern const size_t mips64_global_filter_size;
-
-#endif
diff --git a/libc/stdio/local.h b/libc/stdio/local.h
index a31d7b9..11b136d 100644
--- a/libc/stdio/local.h
+++ b/libc/stdio/local.h
@@ -32,8 +32,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __BIONIC_STDIO_LOCAL_H__
-#define __BIONIC_STDIO_LOCAL_H__
+#pragma once
 
 #include <pthread.h>
 #include <stdbool.h>
@@ -278,5 +277,3 @@
 char* __ldtoa(long double*, int, int, int*, int*, char**);
 
 __END_DECLS
-
-#endif
diff --git a/libc/stdio/wcio.h b/libc/stdio/wcio.h
index 3c4f7a4..047eb77 100644
--- a/libc/stdio/wcio.h
+++ b/libc/stdio/wcio.h
@@ -29,8 +29,7 @@
  * $Citrus$
  */
 
-#ifndef _WCIO_H_
-#define _WCIO_H_
+#pragma once
 
 #include <sys/cdefs.h>
 
@@ -80,5 +79,3 @@
 } while (0)
 
 __END_DECLS
-
-#endif /*_WCIO_H_*/
diff --git a/libc/system_properties/include/system_properties/context_node.h b/libc/system_properties/include/system_properties/context_node.h
index 6a3bbcd..35d0e92 100644
--- a/libc/system_properties/include/system_properties/context_node.h
+++ b/libc/system_properties/include/system_properties/context_node.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef SYSTEM_PROPERTIES_CONTEXT_NODE_H
-#define SYSTEM_PROPERTIES_CONTEXT_NODE_H
+#pragma once
 
 #include "private/bionic_lock.h"
 
@@ -66,5 +65,3 @@
   bool no_access_;
   const char* filename_;
 };
-
-#endif
diff --git a/libc/system_properties/include/system_properties/contexts.h b/libc/system_properties/include/system_properties/contexts.h
index 8f154ed..670f808 100644
--- a/libc/system_properties/include/system_properties/contexts.h
+++ b/libc/system_properties/include/system_properties/contexts.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef SYSTEM_PROPERTIES_CONTEXTS_H
-#define SYSTEM_PROPERTIES_CONTEXTS_H
+#pragma once
 
 #include "prop_area.h"
 #include "prop_info.h"
@@ -44,5 +43,3 @@
   virtual void ResetAccess() = 0;
   virtual void FreeAndUnmap() = 0;
 };
-
-#endif
diff --git a/libc/system_properties/include/system_properties/contexts_pre_split.h b/libc/system_properties/include/system_properties/contexts_pre_split.h
index 14b00f1..6e695e9 100644
--- a/libc/system_properties/include/system_properties/contexts_pre_split.h
+++ b/libc/system_properties/include/system_properties/contexts_pre_split.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef SYSTEM_PROPERTIES_CONTEXTS_PRE_SPLIT_H
-#define SYSTEM_PROPERTIES_CONTEXTS_PRE_SPLIT_H
+#pragma once
 
 #include "contexts.h"
 #include "prop_area.h"
@@ -68,5 +67,3 @@
  private:
   prop_area* pre_split_prop_area_ = nullptr;
 };
-
-#endif
diff --git a/libc/system_properties/include/system_properties/contexts_serialized.h b/libc/system_properties/include/system_properties/contexts_serialized.h
index 010730a..93d6ac1 100644
--- a/libc/system_properties/include/system_properties/contexts_serialized.h
+++ b/libc/system_properties/include/system_properties/contexts_serialized.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef SYSTEM_PROPERTIES_CONTEXTS_SERIALIZED_H
-#define SYSTEM_PROPERTIES_CONTEXTS_SERIALIZED_H
+#pragma once
 
 #include <property_info_parser/property_info_parser.h>
 
@@ -60,5 +59,3 @@
   size_t context_nodes_mmap_size_ = 0;
   prop_area* serial_prop_area_ = nullptr;
 };
-
-#endif
diff --git a/libc/system_properties/include/system_properties/contexts_split.h b/libc/system_properties/include/system_properties/contexts_split.h
index 06c405a..acb18e3 100644
--- a/libc/system_properties/include/system_properties/contexts_split.h
+++ b/libc/system_properties/include/system_properties/contexts_split.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef SYSTEM_PROPERTIES_CONTEXTS_SPLIT_H
-#define SYSTEM_PROPERTIES_CONTEXTS_SPLIT_H
+#pragma once
 
 #include "contexts.h"
 
@@ -58,5 +57,3 @@
   prop_area* serial_prop_area_ = nullptr;
   const char* filename_ = nullptr;
 };
-
-#endif
diff --git a/libc/system_properties/include/system_properties/prop_area.h b/libc/system_properties/include/system_properties/prop_area.h
index a7d5d22..2c25337 100644
--- a/libc/system_properties/include/system_properties/prop_area.h
+++ b/libc/system_properties/include/system_properties/prop_area.h
@@ -26,6 +26,8 @@
  * SUCH DAMAGE.
  */
 
+#pragma once
+
 #include <stdatomic.h>
 #include <stdint.h>
 #include <string.h>
@@ -35,9 +37,6 @@
 
 #include "prop_info.h"
 
-#ifndef SYSTEM_PROPERTIES_PROP_AREA_H
-#define SYSTEM_PROPERTIES_PROP_AREA_H
-
 // Properties are stored in a hybrid trie/binary tree structure.
 // Each property's name is delimited at '.' characters, and the tokens are put
 // into a trie structure.  Siblings at each level of the trie are stored in a
@@ -161,5 +160,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(prop_area);
 };
-
-#endif
diff --git a/libc/system_properties/include/system_properties/prop_info.h b/libc/system_properties/include/system_properties/prop_info.h
index 99bcaaf..a127550 100644
--- a/libc/system_properties/include/system_properties/prop_info.h
+++ b/libc/system_properties/include/system_properties/prop_info.h
@@ -26,15 +26,14 @@
  * SUCH DAMAGE.
  */
 
+#pragma once
+
 #include <stdatomic.h>
 #include <stdint.h>
 #include <sys/system_properties.h>
 
 #include "private/bionic_macros.h"
 
-#ifndef SYSTEM_PROPERTIES_PROP_INFO_H
-#define SYSTEM_PROPERTIES_PROP_INFO_H
-
 // The C11 standard doesn't allow atomic loads from const fields,
 // though C++11 does.  Fudge it until standards get straightened out.
 static inline uint_least32_t load_const_atomic(const atomic_uint_least32_t* s, memory_order mo) {
@@ -88,5 +87,3 @@
 };
 
 static_assert(sizeof(prop_info) == 96, "sizeof struct prop_info must be 96 bytes");
-
-#endif
diff --git a/libc/system_properties/include/system_properties/system_properties.h b/libc/system_properties/include/system_properties/system_properties.h
index 83ac00c..37fe6c0 100644
--- a/libc/system_properties/include/system_properties/system_properties.h
+++ b/libc/system_properties/include/system_properties/system_properties.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef SYSTEM_PROPERTIES_SYSTEM_PROPERTIES_H
-#define SYSTEM_PROPERTIES_SYSTEM_PROPERTIES_H
+#pragma once
 
 #include <stdint.h>
 #include <sys/system_properties.h>
@@ -92,5 +91,3 @@
   bool initialized_;
   char property_filename_[PROP_FILENAME_MAX];
 };
-
-#endif
diff --git a/libm/fpmath.h b/libm/fpmath.h
index 80420e5..854ba11 100644
--- a/libm/fpmath.h
+++ b/libm/fpmath.h
@@ -33,8 +33,7 @@
 // - android uses 128 bits long doubles for LP64, so the structure and macros
 //   were reworked for the quad precision ieee representation.
 
-#ifndef _FPMATH_
-#define _FPMATH_
+#pragma once
 
 #include <endian.h>
 
@@ -92,5 +91,3 @@
 } while(0)
 
 #endif // __LP64__
-
-#endif // _FPMATH_
diff --git a/libm/freebsd-compat.h b/libm/freebsd-compat.h
index ee41e45..0bcc40d 100644
--- a/libm/freebsd-compat.h
+++ b/libm/freebsd-compat.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef _BIONIC_LIBM_FREEBSD_COMPAT_H_included
-#define _BIONIC_LIBM_FREEBSD_COMPAT_H_included
+#pragma once
 
 #include <float.h>
 
@@ -38,5 +37,3 @@
 
 // Similarly rename _scan_nan.
 #define _scan_nan __libm_scan_nan
-
-#endif
diff --git a/linker/linked_list.h b/linker/linked_list.h
index ed2b150..048ea4d 100644
--- a/linker/linked_list.h
+++ b/linker/linked_list.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKED_LIST_H
-#define __LINKED_LIST_H
+#pragma once
 
 #include "private/bionic_macros.h"
 
@@ -259,5 +258,3 @@
   LinkedListEntry<T>* tail_;
   DISALLOW_COPY_AND_ASSIGN(LinkedList);
 };
-
-#endif // __LINKED_LIST_H
diff --git a/linker/linker.h b/linker/linker.h
index 29d40fa..260c89d 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _LINKER_H_
-#define _LINKER_H_
+#pragma once
 
 #include <dlfcn.h>
 #include <android/dlext.h>
@@ -187,5 +186,3 @@
 
 void increment_dso_handle_reference_counter(void* dso_handle);
 void decrement_dso_handle_reference_counter(void* dso_handle);
-
-#endif
diff --git a/linker/linker_allocator.h b/linker/linker_allocator.h
index 7fc6cbf..82e4ef4 100644
--- a/linker/linker_allocator.h
+++ b/linker/linker_allocator.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_ALLOCATOR_H
-#define __LINKER_ALLOCATOR_H
+#pragma once
 
 #include <errno.h>
 #include <stdlib.h>
@@ -152,6 +151,3 @@
   LinkerSmallObjectAllocator* allocators_;
   uint8_t allocators_buf_[sizeof(LinkerSmallObjectAllocator)*kSmallObjectAllocatorsCount];
 };
-
-
-#endif  /* __LINKER_ALLOCATOR_H */
diff --git a/linker/linker_block_allocator.h b/linker/linker_block_allocator.h
index eba1db2..b501659 100644
--- a/linker/linker_block_allocator.h
+++ b/linker/linker_block_allocator.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_BLOCK_ALLOCATOR_H
-#define __LINKER_BLOCK_ALLOCATOR_H
+#pragma once
 
 #include <stdlib.h>
 #include <limits.h>
@@ -89,5 +88,3 @@
   LinkerBlockAllocator block_allocator_;
   DISALLOW_COPY_AND_ASSIGN(LinkerTypeAllocator);
 };
-
-#endif // __LINKER_BLOCK_ALLOCATOR_H
diff --git a/linker/linker_cfi.h b/linker/linker_cfi.h
index e54554f..f3300d6 100644
--- a/linker/linker_cfi.h
+++ b/linker/linker_cfi.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _LINKER_CFI_H_
-#define _LINKER_CFI_H_
+#pragma once
 
 #include "linker.h"
 #include "linker_debug.h"
@@ -103,5 +102,3 @@
 };
 
 CFIShadowWriter* get_cfi_shadow();
-
-#endif // _LINKER_CFI_H_
diff --git a/linker/linker_common_types.h b/linker/linker_common_types.h
index 6afd950..ffa4066 100644
--- a/linker/linker_common_types.h
+++ b/linker/linker_common_types.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_COMMON_TYPES_H
-#define __LINKER_COMMON_TYPES_H
+#pragma once
 
 #include <android/dlext.h>
 #include "linked_list.h"
@@ -65,5 +64,3 @@
 
 typedef LinkedList<soinfo, SoinfoListAllocator> soinfo_list_t;
 typedef LinkedList<android_namespace_t, NamespaceListAllocator> android_namespace_list_t;
-
-#endif  /* __LINKER_COMMON_TYPES_H */
diff --git a/linker/linker_config.h b/linker/linker_config.h
index 0c50d57..e117aea 100644
--- a/linker/linker_config.h
+++ b/linker/linker_config.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _LINKER_CONFIG_H_
-#define _LINKER_CONFIG_H_
+#pragma once
 
 #include <android/api-level.h>
 
@@ -171,5 +170,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(Config);
 };
-
-#endif /* _LINKER_CONFIG_H_ */
diff --git a/linker/linker_debug.h b/linker/linker_debug.h
index 7ceab08..862ea12 100644
--- a/linker/linker_debug.h
+++ b/linker/linker_debug.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _LINKER_DEBUG_H_
-#define _LINKER_DEBUG_H_
+#pragma once
 
 // You can increase the verbosity of debug traces by defining the LD_DEBUG
 // environment variable to a numeric value from 0 to 2 (corresponding to
@@ -102,5 +101,3 @@
 #define MARK(x) do {} while (0)
 
 #endif
-
-#endif /* _LINKER_DEBUG_H_ */
diff --git a/linker/linker_dlwarning.h b/linker/linker_dlwarning.h
index 68827f7..af26824 100644
--- a/linker/linker_dlwarning.h
+++ b/linker/linker_dlwarning.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_DLWARNING_H
-#define __LINKER_DLWARNING_H
+#pragma once
 
 void add_dlwarning(const char* sopath, const char* message, const char* value = nullptr);
 
@@ -36,5 +35,3 @@
 // is used to avoid forcing user into saving the message
 // to a global variable.
 void get_dlwarning(void* user_data, void (*f)(void*, const char*));
-
-#endif  /* __LINKER_DLWARNING_H */
diff --git a/linker/linker_gdb_support.h b/linker/linker_gdb_support.h
index 6709da1..4ae18ee 100644
--- a/linker/linker_gdb_support.h
+++ b/linker/linker_gdb_support.h
@@ -25,8 +25,8 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#ifndef __LINKER_GDB_SUPPORT_H
-#define __LINKER_GDB_SUPPORT_H
+
+#pragma once
 
 #include <link.h>
 #include <sys/cdefs.h>
@@ -42,5 +42,3 @@
 extern struct r_debug _r_debug;
 
 __END_DECLS
-
-#endif
diff --git a/linker/linker_globals.h b/linker/linker_globals.h
index 11ccbd5..b470918 100644
--- a/linker/linker_globals.h
+++ b/linker/linker_globals.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_GLOBALS_H
-#define __LINKER_GLOBALS_H
+#pragma once
 
 #include <link.h>
 #include <stddef.h>
@@ -86,5 +85,3 @@
  private:
   std::string saved_error_msg_;
 };
-
-#endif  /* __LINKER_GLOBALS_H */
diff --git a/linker/linker_logger.h b/linker/linker_logger.h
index 3e53f74..9ce438e 100644
--- a/linker/linker_logger.h
+++ b/linker/linker_logger.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _LINKER_LOGGER_H_
-#define _LINKER_LOGGER_H_
+#pragma once
 
 #include <stdlib.h>
 #include <limits.h>
@@ -61,5 +60,3 @@
 // If the system property debug.ld.greylist_disabled is true, we'll not use the greylist
 // regardless of API level.
 extern bool g_greylist_disabled;
-
-#endif /* _LINKER_LOGGER_H_ */
diff --git a/linker/linker_main.h b/linker/linker_main.h
index 5641696..8d486e8 100644
--- a/linker/linker_main.h
+++ b/linker/linker_main.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_MAIN_H
-#define __LINKER_MAIN_H
+#pragma once
 
 #include <android/dlext.h>
 
@@ -71,5 +70,3 @@
 bool solist_remove_soinfo(soinfo* si);
 soinfo* solist_get_head();
 soinfo* solist_get_somain();
-
-#endif
diff --git a/linker/linker_mapped_file_fragment.h b/linker/linker_mapped_file_fragment.h
index 0bfc7a3..f7872bd 100644
--- a/linker/linker_mapped_file_fragment.h
+++ b/linker/linker_mapped_file_fragment.h
@@ -25,8 +25,8 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#ifndef LINKER_MAPPED_FILE_FRAGMENT_H
-#define LINKER_MAPPED_FILE_FRAGMENT_H
+
+#pragma once
 
 #include <unistd.h>
 
@@ -49,5 +49,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(MappedFileFragment);
 };
-
-#endif /* LINKER_MAPPED_FILE_FRAGMENT_H */
diff --git a/linker/linker_namespaces.h b/linker/linker_namespaces.h
index a7fe0d5..03520d7 100644
--- a/linker/linker_namespaces.h
+++ b/linker/linker_namespaces.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_NAMESPACES_H
-#define __LINKER_NAMESPACES_H
+#pragma once
 
 #include "linker_common_types.h"
 
@@ -164,5 +163,3 @@
 
   DISALLOW_COPY_AND_ASSIGN(android_namespace_t);
 };
-
-#endif  /* __LINKER_NAMESPACES_H */
diff --git a/linker/linker_phdr.h b/linker/linker_phdr.h
index d6276ed..9b9ce94 100644
--- a/linker/linker_phdr.h
+++ b/linker/linker_phdr.h
@@ -25,8 +25,8 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#ifndef LINKER_PHDR_H
-#define LINKER_PHDR_H
+
+#pragma once
 
 /* Declarations related to the ELF program header table and segments.
  *
@@ -134,5 +134,3 @@
 
 const char* phdr_table_get_interpreter_name(const ElfW(Phdr) * phdr_table, size_t phdr_count,
                                             ElfW(Addr) load_bias);
-
-#endif /* LINKER_PHDR_H */
diff --git a/linker/linker_reloc_iterators.h b/linker/linker_reloc_iterators.h
index 6340924..b162684 100644
--- a/linker/linker_reloc_iterators.h
+++ b/linker/linker_reloc_iterators.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_RELOC_ITERATORS_H
-#define __LINKER_RELOC_ITERATORS_H
+#pragma once
 
 #include "linker.h"
 
@@ -173,5 +172,3 @@
   size_t relocation_group_index_;
   rel_t reloc_;
 };
-
-#endif  // __LINKER_RELOC_ITERATORS_H
diff --git a/linker/linker_relocs.h b/linker/linker_relocs.h
index ed00594..4bab0e0 100644
--- a/linker/linker_relocs.h
+++ b/linker/linker_relocs.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_RELOCS_H
-#define __LINKER_RELOCS_H
+#pragma once
 
 #include <elf.h>
 
@@ -62,5 +61,3 @@
 #define R_GENERIC_IRELATIVE R_X86_64_IRELATIVE
 
 #endif
-
-#endif // __LINKER_RELOCS_H
diff --git a/linker/linker_sleb128.h b/linker/linker_sleb128.h
index 01e127d..6bb3199 100644
--- a/linker/linker_sleb128.h
+++ b/linker/linker_sleb128.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _LINKER_SLEB128_H
-#define _LINKER_SLEB128_H
+#pragma once
 
 #include <stdint.h>
 
@@ -70,5 +69,3 @@
   const uint8_t* current_;
   const uint8_t* const end_;
 };
-
-#endif // __LINKER_SLEB128_H
diff --git a/linker/linker_soinfo.h b/linker/linker_soinfo.h
index 447c7c3..6e1f005 100644
--- a/linker/linker_soinfo.h
+++ b/linker/linker_soinfo.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_SOINFO_H
-#define __LINKER_SOINFO_H
+#pragma once
 
 #include <link.h>
 
@@ -386,5 +385,3 @@
     }
   }
 }
-
-#endif  /* __LINKER_SOINFO_H */
diff --git a/linker/linker_utils.h b/linker/linker_utils.h
index e104a25..214646c 100644
--- a/linker/linker_utils.h
+++ b/linker/linker_utils.h
@@ -26,8 +26,7 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __LINKER_UTILS_H
-#define __LINKER_UTILS_H
+#pragma once
 
 #include <string>
 #include <vector>
@@ -56,5 +55,3 @@
 off64_t page_start(off64_t offset);
 size_t page_offset(off64_t offset);
 bool safe_add(off64_t* out, off64_t a, size_t b);
-
-#endif