--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -551,7 +551,7 @@ case ${target} in
 esac
 
 # Common C libraries.
-tm_defines="$tm_defines LIBC_GLIBC=1 LIBC_UCLIBC=2 LIBC_BIONIC=3"
+tm_defines="$tm_defines LIBC_GLIBC=1 LIBC_UCLIBC=2 LIBC_BIONIC=3 LIBC_MUSL=4"
 
 # Common parts for widely ported systems.
 case ${target} in
@@ -654,6 +654,9 @@ case ${target} in
     *-*-*uclibc*)
       tm_defines="$tm_defines DEFAULT_LIBC=LIBC_UCLIBC"
       ;;
+    *-*-*musl*)
+      tm_defines="$tm_defines DEFAULT_LIBC=LIBC_MUSL"
+      ;;
     *)
       tm_defines="$tm_defines DEFAULT_LIBC=LIBC_GLIBC"
       ;;
--- a/gcc/config/arm/linux-eabi.h
+++ b/gcc/config/arm/linux-eabi.h
@@ -77,6 +77,10 @@
     %{mfloat-abi=soft*:" GLIBC_DYNAMIC_LINKER_SOFT_FLOAT "} \
     %{!mfloat-abi=*:" GLIBC_DYNAMIC_LINKER_DEFAULT "}"
 
+/* musl has no "classic" (i.e. broken) mode */
+#undef  MUSL_DYNAMIC_LINKER
+#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-arm.so.1"
+
 /* At this point, bpabi.h will have clobbered LINK_SPEC.  We want to
    use the GNU/Linux version, not the generic BPABI version.  */
 #undef  LINK_SPEC
--- a/gcc/config/i386/linux.h
+++ b/gcc/config/i386/linux.h
@@ -21,3 +21,4 @@ along with GCC; see the file COPYING3.
 
 #define GNU_USER_LINK_EMULATION "elf_i386"
 #define GLIBC_DYNAMIC_LINKER "/lib/ld-linux.so.2"
+#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-i386.so.1"
--- a/gcc/config/i386/linux64.h
+++ b/gcc/config/i386/linux64.h
@@ -30,3 +30,7 @@ see the files COPYING3 and COPYING.RUNTI
 #define GLIBC_DYNAMIC_LINKER32 "/lib/ld-linux.so.2"
 #define GLIBC_DYNAMIC_LINKER64 "/lib64/ld-linux-x86-64.so.2"
 #define GLIBC_DYNAMIC_LINKERX32 "/libx32/ld-linux-x32.so.2"
+
+#define MUSL_DYNAMIC_LINKER32 "/lib/ld-musl-i386.so.1"
+#define MUSL_DYNAMIC_LINKER64 "/lib/ld-musl-x86_64.so.1"
+#define MUSL_DYNAMIC_LINKERX32 "/lib/ld-musl-x32.so.1"
--- a/gcc/config/linux.h
+++ b/gcc/config/linux.h
@@ -32,10 +32,12 @@ see the files COPYING3 and COPYING.RUNTI
 #define OPTION_GLIBC  (DEFAULT_LIBC == LIBC_GLIBC)
 #define OPTION_UCLIBC (DEFAULT_LIBC == LIBC_UCLIBC)
 #define OPTION_BIONIC (DEFAULT_LIBC == LIBC_BIONIC)
+#define OPTION_MUSL   (DEFAULT_LIBC == LIBC_MUSL)
 #else
 #define OPTION_GLIBC  (linux_libc == LIBC_GLIBC)
 #define OPTION_UCLIBC (linux_libc == LIBC_UCLIBC)
 #define OPTION_BIONIC (linux_libc == LIBC_BIONIC)
+#define OPTION_MUSL   (linux_libc == LIBC_MUSL)
 #endif
 
 #define GNU_USER_TARGET_OS_CPP_BUILTINS()			\
@@ -53,18 +55,21 @@ see the files COPYING3 and COPYING.RUNTI
    uClibc or Bionic is the default C library and whether
    -muclibc or -mglibc or -mbionic has been passed to change the default.  */
 
-#define CHOOSE_DYNAMIC_LINKER1(LIBC1, LIBC2, LIBC3, LD1, LD2, LD3)	\
-  "%{" LIBC2 ":" LD2 ";:%{" LIBC3 ":" LD3 ";:" LD1 "}}"
+#define CHOOSE_DYNAMIC_LINKER1(LIBC1, LIBC2, LIBC3, LIBC4, LD1, LD2, LD3, LD4)	\
+  "%{" LIBC2 ":" LD2 ";:%{" LIBC3 ":" LD3 ";:%{" LIBC4 ":" LD4 ";:" LD1 "}}}"
 
 #if DEFAULT_LIBC == LIBC_GLIBC
-#define CHOOSE_DYNAMIC_LINKER(G, U, B) \
-  CHOOSE_DYNAMIC_LINKER1 ("mglibc", "muclibc", "mbionic", G, U, B)
+#define CHOOSE_DYNAMIC_LINKER(G, U, B, M) \
+  CHOOSE_DYNAMIC_LINKER1 ("mglibc", "muclibc", "mbionic", "mmusl", G, U, B, M)
 #elif DEFAULT_LIBC == LIBC_UCLIBC
-#define CHOOSE_DYNAMIC_LINKER(G, U, B) \
-  CHOOSE_DYNAMIC_LINKER1 ("muclibc", "mglibc", "mbionic", U, G, B)
+#define CHOOSE_DYNAMIC_LINKER(G, U, B, M) \
+  CHOOSE_DYNAMIC_LINKER1 ("muclibc", "mglibc", "mbionic", "mmusl", U, G, B, M)
 #elif DEFAULT_LIBC == LIBC_BIONIC
-#define CHOOSE_DYNAMIC_LINKER(G, U, B) \
-  CHOOSE_DYNAMIC_LINKER1 ("mbionic", "mglibc", "muclibc", B, G, U)
+#define CHOOSE_DYNAMIC_LINKER(G, U, B, M) \
+  CHOOSE_DYNAMIC_LINKER1 ("mbionic", "mglibc", "muclibc", "mmusl", B, G, U, M)
+#elif DEFAULT_LIBC == LIBC_MUSL
+#define CHOOSE_DYNAMIC_LINKER(G, U, B, M) \
+  CHOOSE_DYNAMIC_LINKER1 ("mmusl", "mglibc", "muclibc", "mbionic", M, G, U, B)
 #else
 #error "Unsupported DEFAULT_LIBC"
 #endif /* DEFAULT_LIBC */
@@ -84,16 +89,16 @@ see the files COPYING3 and COPYING.RUNTI
 
 #define GNU_USER_DYNAMIC_LINKER						\
   CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER, UCLIBC_DYNAMIC_LINKER,	\
-			 BIONIC_DYNAMIC_LINKER)
+			 BIONIC_DYNAMIC_LINKER, MUSL_DYNAMIC_LINKER)
 #define GNU_USER_DYNAMIC_LINKER32					\
   CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER32, UCLIBC_DYNAMIC_LINKER32, \
-			 BIONIC_DYNAMIC_LINKER32)
+			 BIONIC_DYNAMIC_LINKER32, MUSL_DYNAMIC_LINKER32)
 #define GNU_USER_DYNAMIC_LINKER64					\
   CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER64, UCLIBC_DYNAMIC_LINKER64, \
-			 BIONIC_DYNAMIC_LINKER64)
+			 BIONIC_DYNAMIC_LINKER64, MUSL_DYNAMIC_LINKER64)
 #define GNU_USER_DYNAMIC_LINKERX32					\
   CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKERX32, UCLIBC_DYNAMIC_LINKERX32, \
-			 BIONIC_DYNAMIC_LINKERX32)
+			 BIONIC_DYNAMIC_LINKERX32, MUSL_DYNAMIC_LINKERX32)
 
 /* Determine whether the entire c99 runtime
    is present in the runtime library.  */
--- a/gcc/config/linux.opt
+++ b/gcc/config/linux.opt
@@ -30,3 +30,7 @@ Use GNU C library
 muclibc
 Target Report RejectNegative Var(linux_libc,LIBC_UCLIBC) Negative(mbionic)
 Use uClibc C library
+
+mmusl
+Target Report RejectNegative Var(linux_libc,LIBC_MUSL) Negative(mglibc)
+Use musl C library
--- a/gcc/config/mips/linux.h
+++ b/gcc/config/mips/linux.h
@@ -18,3 +18,5 @@ along with GCC; see the file COPYING3.
 <http://www.gnu.org/licenses/>.  */
 
 #define GLIBC_DYNAMIC_LINKER "/lib/ld.so.1"
+
+#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-mips.so.1"
--- a/gcc/config/rs6000/linux64.h
+++ b/gcc/config/rs6000/linux64.h
@@ -354,17 +354,21 @@ extern int dot_symbols;
 #define GLIBC_DYNAMIC_LINKER64 "/lib64/ld64.so.1"
 #define UCLIBC_DYNAMIC_LINKER32 "/lib/ld-uClibc.so.0"
 #define UCLIBC_DYNAMIC_LINKER64 "/lib/ld64-uClibc.so.0"
+#define MUSL_DYNAMIC_LINKER32 "/lib/ld-musl-powerpc.so.1"
+#define MUSL_DYNAMIC_LINKER64 "/lib/ld-musl-powerpc64.so.1"
 #if DEFAULT_LIBC == LIBC_UCLIBC
-#define CHOOSE_DYNAMIC_LINKER(G, U) "%{mglibc:" G ";:" U "}"
+#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{mglibc:" G ";:%{mmusl:" M ";:" U "}}"
 #elif DEFAULT_LIBC == LIBC_GLIBC
-#define CHOOSE_DYNAMIC_LINKER(G, U) "%{muclibc:" U ";:" G "}"
+#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{muclibc:" U ";:%{mmusl:" M ";:" G "}}"
+#elif DEFAULT_LIBC == LIBC_MUSL
+#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{mglibc:" G ";:%{muclibc:" U ";:" M "}}"
 #else
 #error "Unsupported DEFAULT_LIBC"
 #endif
 #define GNU_USER_DYNAMIC_LINKER32 \
-  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER32, UCLIBC_DYNAMIC_LINKER32)
+  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER32, UCLIBC_DYNAMIC_LINKER32, MUSL_DYNAMIC_LINKER32)
 #define GNU_USER_DYNAMIC_LINKER64 \
-  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER64, UCLIBC_DYNAMIC_LINKER64)
+  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER64, UCLIBC_DYNAMIC_LINKER64, MUSL_DYNAMIC_LINKER64)
 
 #undef  DEFAULT_ASM_ENDIAN
 #if (TARGET_DEFAULT & MASK_LITTLE_ENDIAN)
--- a/gcc/config/rs6000/sysv4.h
+++ b/gcc/config/rs6000/sysv4.h
@@ -778,15 +778,18 @@ ENDIAN_SELECT(" -mbig", " -mlittle", DEF
 
 #define GLIBC_DYNAMIC_LINKER "/lib/ld.so.1"
 #define UCLIBC_DYNAMIC_LINKER "/lib/ld-uClibc.so.0"
+#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-powerpc.so.1"
 #if DEFAULT_LIBC == LIBC_UCLIBC
-#define CHOOSE_DYNAMIC_LINKER(G, U) "%{mglibc:" G ";:" U "}"
+#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{mglibc:" G ";:%{mmusl:" M ";:" U "}}"
+#elif DEFAULT_LIBC == LIBC_MUSL
+#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{mglibc:" G ";:%{muclibc:" U ";:" M "}}"
 #elif !defined (DEFAULT_LIBC) || DEFAULT_LIBC == LIBC_GLIBC
-#define CHOOSE_DYNAMIC_LINKER(G, U) "%{muclibc:" U ";:" G "}"
+#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{muclibc:" U ";:%{mmusl:" M ";:" G "}}"
 #else
 #error "Unsupported DEFAULT_LIBC"
 #endif
 #define GNU_USER_DYNAMIC_LINKER \
-  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER, UCLIBC_DYNAMIC_LINKER)
+  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER, UCLIBC_DYNAMIC_LINKER, MUSL_DYNAMIC_LINKER)
 
 #define LINK_OS_LINUX_SPEC "-m elf32ppclinux %{!shared: %{!static: \
   %{rdynamic:-export-dynamic} \
--- a/gcc/ginclude/stddef.h
+++ b/gcc/ginclude/stddef.h
@@ -181,6 +181,7 @@ typedef __PTRDIFF_TYPE__ ptrdiff_t;
 #ifndef _GCC_SIZE_T
 #ifndef _SIZET_
 #ifndef __size_t
+#ifndef __DEFINED_size_t /* musl */
 #define __size_t__	/* BeOS */
 #define __SIZE_T__	/* Cray Unicos/Mk */
 #define _SIZE_T
@@ -197,6 +198,7 @@ typedef __PTRDIFF_TYPE__ ptrdiff_t;
 #define ___int_size_t_h
 #define _GCC_SIZE_T
 #define _SIZET_
+#define __DEFINED_size_t /* musl */
 #if (defined (__FreeBSD__) && (__FreeBSD__ >= 5)) \
   || defined(__FreeBSD_kernel__)
 /* __size_t is a typedef on FreeBSD 5, must not trash it. */
@@ -214,6 +216,7 @@ typedef __SIZE_TYPE__ size_t;
 typedef long ssize_t;
 #endif /* __BEOS__ */
 #endif /* !(defined (__GNUG__) && defined (size_t)) */
+#endif /* __DEFINED_size_t */
 #endif /* __size_t */
 #endif /* _SIZET_ */
 #endif /* _GCC_SIZE_T */
--- a/libgomp/config/posix/time.c
+++ b/libgomp/config/posix/time.c
@@ -28,6 +28,8 @@
    The following implementation uses the most simple POSIX routines.
    If present, POSIX 4 clocks should be used instead.  */
 
+#define _POSIX_C_SOURCE 199309L /* for clocks */
+
 #include "libgomp.h"
 #include <unistd.h>
 #if TIME_WITH_SYS_TIME
--- a/libitm/config/arm/hwcap.cc
+++ b/libitm/config/arm/hwcap.cc
@@ -40,7 +40,11 @@ int GTM_hwcap HIDDEN = 0
 
 #ifdef __linux__
 #include <unistd.h>
+#ifdef __GLIBC__
 #include <sys/fcntl.h>
+#else
+#include <fcntl.h>
+#endif
 #include <elf.h>
 
 static void __attribute__((constructor))
--- a/libitm/config/linux/x86/tls.h
+++ b/libitm/config/linux/x86/tls.h
@@ -25,16 +25,19 @@
 #ifndef LIBITM_X86_TLS_H
 #define LIBITM_X86_TLS_H 1
 
-#if defined(__GLIBC_PREREQ) && __GLIBC_PREREQ(2, 10)
+#if defined(__GLIBC_PREREQ)
+#if __GLIBC_PREREQ(2, 10)
 /* Use slots in the TCB head rather than __thread lookups.
    GLIBC has reserved words 10 through 13 for TM.  */
 #define HAVE_ARCH_GTM_THREAD 1
 #define HAVE_ARCH_GTM_THREAD_DISP 1
 #endif
+#endif
 
 #include "config/generic/tls.h"
 
-#if defined(__GLIBC_PREREQ) && __GLIBC_PREREQ(2, 10)
+#if defined(__GLIBC_PREREQ)
+#if __GLIBC_PREREQ(2, 10)
 namespace GTM HIDDEN {
 
 #ifdef __x86_64__
@@ -101,5 +104,6 @@ static inline void set_abi_disp(struct a
 
 } // namespace GTM
 #endif /* >= GLIBC 2.10 */
+#endif
 
 #endif // LIBITM_X86_TLS_H
--- a/libstdc++-v3/configure.host
+++ b/libstdc++-v3/configure.host
@@ -264,6 +264,13 @@ case "${host_os}" in
     os_include_dir="os/bsd/freebsd"
     ;;
   gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu)
+    # check for musl by target
+    case "${host_os}" in
+      *-musl*)
+        os_include_dir="os/generic"
+        ;;
+      *)
+
     if [ "$uclibc" = "yes" ]; then
       os_include_dir="os/uclibc"
     elif [ "$bionic" = "yes" ]; then
@@ -272,6 +279,9 @@ case "${host_os}" in
       os_include_dir="os/gnu-linux"
     fi
     ;;
+
+    esac
+    ;;
   hpux*)
     os_include_dir="os/hpux"
     ;;
--- a/gcc/config/mips/linux64.h
+++ b/gcc/config/mips/linux64.h
@@ -27,6 +27,9 @@ along with GCC; see the file COPYING3.
 #define GLIBC_DYNAMIC_LINKERN32 "/lib32/ld.so.1"
 #define UCLIBC_DYNAMIC_LINKERN32 "/lib32/ld-uClibc.so.0"
 #define BIONIC_DYNAMIC_LINKERN32 "/system/bin/linker32"
+#define MUSL_DYNAMIC_LINKERN32 "/lib/ld-musl-mips.so.1"
+#define MUSL_DYNAMIC_LINKER32 "/lib/ld-musl-mips.so.1"
+#define MUSL_DYNAMIC_LINKER64 "/lib/ld-musl-mips.so.1"
 #define GNU_USER_DYNAMIC_LINKERN32 \
   CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKERN32, UCLIBC_DYNAMIC_LINKERN32, \
-			 BIONIC_DYNAMIC_LINKERN32)
+			 BIONIC_DYNAMIC_LINKERN32, MUSL_DYNAMIC_LINKERN32)
--- a/gcc/config/sparc/linux64.h
+++ b/gcc/config/sparc/linux64.h
@@ -95,6 +95,9 @@ along with GCC; see the file COPYING3.
 #define GLIBC_DYNAMIC_LINKER32 "/lib/ld-linux.so.2"
 #define GLIBC_DYNAMIC_LINKER64 "/lib64/ld-linux.so.2"
 
+#define MUSL_DYNAMIC_LINKER32 "/lib/ld-musl-sparc.so.1"
+#define MUSL_DYNAMIC_LINKER64 "/lib/ld-musl-sparc.so.1"
+
 #ifdef SPARC_BI_ARCH
 
 #undef SUBTARGET_EXTRA_SPECS
