Merge branch 'master' into devel/coarray_native.

Merge into devel/coarray_native to prepare for later merging of
coarray_native with master.

8 files changed, 128 insertions, 71 deletions

diff --git a/libbacktrace/ChangeLog b/libbacktrace/ChangeLog
index b6fbe28..528b2b0 100644
--- a/libbacktrace/ChangeLog
+++ b/libbacktrace/ChangeLog
@@ -1,3 +1,28 @@
+2020-10-20  Ian Lance Taylor  <iant@golang.org>
+
+	* internal.h (ATTRIBUTE_FALLTHROUGH): Define.
+	* elf.c (elf_zlib_inflate): Use ATTRIBUTE_FALLTHROUGH.
+
+2020-09-28  Ian Lance Taylor  <iant@golang.org>
+
+	PR libbacktrace/97082
+	* Makefile.am (check_DATA): Add mtest.dSYM if USE_DSYMUTIL.
+	* Makefile.in: Regenerate.
+
+2020-09-28  Ian Lance Taylor  <iant@golang.org>
+
+	PR libbacktrace/97227
+	* configure.ac (USE_DSYMUTIL): Define instead of HAVE_DSYMUTIL.
+	* Makefile.am: Change all uses of HAVE_DSYMUTIL to USE_DSYMUTIL.
+	* configure: Regenerate.
+	* Makefile.in: Regenerate.
+
+2020-09-23  Ian Lance Taylor  <iant@golang.org>
+
+	* dwarf.c (report_inlined_functions): Handle PC == -1 and PC ==
+	p->low.
+	(dwarf_lookup_pc): Likewise.
+
 2020-09-17  Ian Lance Taylor  <iant@golang.org>
 
 	PR libbacktrace/97080
diff --git a/libbacktrace/Makefile.am b/libbacktrace/Makefile.am
index 4d34938..5899a21 100644
--- a/libbacktrace/Makefile.am
+++ b/libbacktrace/Makefile.am
@@ -100,12 +100,12 @@ check_DATA =
 # Flags to use when compiling test programs.
 libbacktrace_TEST_CFLAGS = $(EXTRA_FLAGS) $(WARN_FLAGS) -g
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 
 %.dSYM: %
 	$(DSYMUTIL) $<
 
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 if NATIVE
 check_LTLIBRARIES = libbacktrace_alloc.la
@@ -237,9 +237,9 @@ allocfail.sh: allocfail
 
 TESTS += allocfail.sh
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += allocfail.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 if HAVE_ELF
 if HAVE_OBJCOPY_DEBUGLINK
@@ -273,9 +273,9 @@ btest_LDADD = libbacktrace.la
 
 BUILDTESTS += btest
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += btest.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 if HAVE_ELF
 
@@ -293,9 +293,9 @@ btest_alloc_LDADD = libbacktrace_alloc.la
 
 BUILDTESTS += btest_alloc
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += btest_alloc.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 if HAVE_DWZ
 
@@ -323,9 +323,9 @@ stest_LDADD = libbacktrace.la
 
 BUILDTESTS += stest
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += stest.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 stest_alloc_SOURCES = $(stest_SOURCES)
 stest_alloc_CFLAGS = $(libbacktrace_TEST_CFLAGS)
@@ -333,9 +333,9 @@ stest_alloc_LDADD = libbacktrace_alloc.la
 
 BUILDTESTS += stest_alloc
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += stest_alloc.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 if HAVE_ELF
 
@@ -366,17 +366,17 @@ edtest_LDADD = libbacktrace.la
 
 BUILDTESTS += edtest
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += edtest.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 edtest_alloc_SOURCES = $(edtest_SOURCES)
 edtest_alloc_CFLAGS = $(libbacktrace_TEST_CFLAGS)
 edtest_alloc_LDADD = libbacktrace_alloc.la
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += edtest_alloc.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 BUILDTESTS += edtest_alloc
 
@@ -394,9 +394,9 @@ ttest_SOURCES = ttest.c testlib.c
 ttest_CFLAGS = $(libbacktrace_TEST_CFLAGS) -pthread
 ttest_LDADD = libbacktrace.la
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += ttest.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 BUILDTESTS += ttest_alloc
 
@@ -404,9 +404,9 @@ ttest_alloc_SOURCES = $(ttest_SOURCES)
 ttest_alloc_CFLAGS = $(ttest_CFLAGS)
 ttest_alloc_LDADD = libbacktrace_alloc.la
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += ttest_alloc.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 endif HAVE_PTHREAD
 
@@ -462,9 +462,9 @@ dwarf5_LDADD = libbacktrace.la
 
 BUILDTESTS += dwarf5
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += dwarf5.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 dwarf5_alloc_SOURCES = $(dwarf5_SOURCES)
 dwarf5_alloc_CFLAGS = $(dwarf5_CFLAGS)
@@ -472,9 +472,9 @@ dwarf5_alloc_LDADD = libbacktrace_alloc.la
 
 BUILDTESTS += dwarf5_alloc
 
-if HAVE_DSYMUTIL
+if USE_DSYMUTIL
 check_DATA += dwarf5_alloc.dSYM
-endif HAVE_DSYMUTIL
+endif USE_DSYMUTIL
 
 endif
 
@@ -484,6 +484,10 @@ mtest_LDADD = libbacktrace.la
 
 BUILDTESTS += mtest
 
+if USE_DSYMUTIL
+check_DATA += mtest.dSYM
+endif USE_DSYMUTIL
+
 if HAVE_MINIDEBUG
 
 TESTS += mtest_minidebug
diff --git a/libbacktrace/Makefile.in b/libbacktrace/Makefile.in
index 201cee3..2f5fdb1 100644
--- a/libbacktrace/Makefile.in
+++ b/libbacktrace/Makefile.in
@@ -124,17 +124,17 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 	$(am__EXEEXT_14)
 TESTS = $(am__append_4) $(am__append_7) $(am__append_9) \
 	$(am__append_12) $(am__append_13) $(am__append_20) \
-	$(am__append_25) $(am__EXEEXT_14)
+	$(am__append_26) $(am__EXEEXT_14)
 @HAVE_ELF_TRUE@@HAVE_OBJCOPY_DEBUGLINK_TRUE@@NATIVE_TRUE@am__append_1 = libbacktrace_elf_for_test.la
 @NATIVE_TRUE@am__append_2 = test_elf_32 test_elf_64 test_macho \
 @NATIVE_TRUE@	test_xcoff_32 test_xcoff_64 test_pecoff \
 @NATIVE_TRUE@	test_unknown unittest unittest_alloc btest
 @NATIVE_TRUE@am__append_3 = allocfail
 @NATIVE_TRUE@am__append_4 = allocfail.sh
-@HAVE_DSYMUTIL_TRUE@@NATIVE_TRUE@am__append_5 = allocfail.dSYM \
-@HAVE_DSYMUTIL_TRUE@@NATIVE_TRUE@	btest.dSYM btest_alloc.dSYM \
-@HAVE_DSYMUTIL_TRUE@@NATIVE_TRUE@	stest.dSYM stest_alloc.dSYM \
-@HAVE_DSYMUTIL_TRUE@@NATIVE_TRUE@	edtest.dSYM edtest_alloc.dSYM
+@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@am__append_5 = allocfail.dSYM \
+@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@	btest.dSYM btest_alloc.dSYM \
+@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@	stest.dSYM stest_alloc.dSYM \
+@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@	edtest.dSYM edtest_alloc.dSYM
 @HAVE_ELF_TRUE@@HAVE_OBJCOPY_DEBUGLINK_TRUE@@NATIVE_TRUE@am__append_6 = b2test
 @HAVE_ELF_TRUE@@HAVE_OBJCOPY_DEBUGLINK_TRUE@@NATIVE_TRUE@am__append_7 = b2test_buildid
 @HAVE_DWZ_TRUE@@HAVE_ELF_TRUE@@HAVE_OBJCOPY_DEBUGLINK_TRUE@@NATIVE_TRUE@am__append_8 = b3test
@@ -148,20 +148,23 @@ TESTS = $(am__append_4) $(am__append_7) $(am__append_9) \
 @HAVE_ELF_TRUE@@NATIVE_TRUE@am__append_16 = ztest ztest_alloc
 @NATIVE_TRUE@am__append_17 = edtest edtest_alloc
 @HAVE_PTHREAD_TRUE@@NATIVE_TRUE@am__append_18 = ttest ttest_alloc
-@HAVE_DSYMUTIL_TRUE@@HAVE_PTHREAD_TRUE@@NATIVE_TRUE@am__append_19 = ttest.dSYM \
-@HAVE_DSYMUTIL_TRUE@@HAVE_PTHREAD_TRUE@@NATIVE_TRUE@	ttest_alloc.dSYM
+@HAVE_PTHREAD_TRUE@@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@am__append_19 =  \
+@HAVE_PTHREAD_TRUE@@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@	ttest.dSYM \
+@HAVE_PTHREAD_TRUE@@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@	ttest_alloc.dSYM
 @HAVE_OBJCOPY_DEBUGLINK_TRUE@@NATIVE_TRUE@am__append_20 = btest_gnudebuglink
 @HAVE_COMPRESSED_DEBUG_TRUE@@NATIVE_TRUE@am__append_21 = ctestg ctesta \
 @HAVE_COMPRESSED_DEBUG_TRUE@@NATIVE_TRUE@	ctestg_alloc \
 @HAVE_COMPRESSED_DEBUG_TRUE@@NATIVE_TRUE@	ctesta_alloc
 @HAVE_DWARF5_TRUE@@NATIVE_TRUE@am__append_22 = dwarf5 dwarf5_alloc
-@HAVE_DSYMUTIL_TRUE@@HAVE_DWARF5_TRUE@@NATIVE_TRUE@am__append_23 = dwarf5.dSYM \
-@HAVE_DSYMUTIL_TRUE@@HAVE_DWARF5_TRUE@@NATIVE_TRUE@	dwarf5_alloc.dSYM
+@HAVE_DWARF5_TRUE@@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@am__append_23 =  \
+@HAVE_DWARF5_TRUE@@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@	dwarf5.dSYM \
+@HAVE_DWARF5_TRUE@@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@	dwarf5_alloc.dSYM
 @NATIVE_TRUE@am__append_24 = mtest
-@HAVE_MINIDEBUG_TRUE@@NATIVE_TRUE@am__append_25 = mtest_minidebug
-@HAVE_ELF_TRUE@@HAVE_LIBLZMA_TRUE@am__append_26 = -llzma
+@NATIVE_TRUE@@USE_DSYMUTIL_TRUE@am__append_25 = mtest.dSYM
+@HAVE_MINIDEBUG_TRUE@@NATIVE_TRUE@am__append_26 = mtest_minidebug
 @HAVE_ELF_TRUE@@HAVE_LIBLZMA_TRUE@am__append_27 = -llzma
-@HAVE_ELF_TRUE@am__append_28 = xztest xztest_alloc
+@HAVE_ELF_TRUE@@HAVE_LIBLZMA_TRUE@am__append_28 = -llzma
+@HAVE_ELF_TRUE@am__append_29 = xztest xztest_alloc
 subdir = .
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps = $(top_srcdir)/../config/cet.m4 \
@@ -989,10 +992,11 @@ libbacktrace_la_DEPENDENCIES = $(libbacktrace_la_LIBADD)
 BUILDTESTS = $(am__append_2) $(am__append_10) $(am__append_11) \
 	$(am__append_16) $(am__append_17) $(am__append_18) \
 	$(am__append_21) $(am__append_22) $(am__append_24) \
-	$(am__append_28)
+	$(am__append_29)
 
 # Add a file to this variable if you want it to be built for testing.
-check_DATA = $(am__append_5) $(am__append_19) $(am__append_23)
+check_DATA = $(am__append_5) $(am__append_19) $(am__append_23) \
+	$(am__append_25)
 
 # Flags to use when compiling test programs.
 libbacktrace_TEST_CFLAGS = $(EXTRA_FLAGS) $(WARN_FLAGS) -g
@@ -1119,12 +1123,12 @@ libbacktrace_TEST_CFLAGS = $(EXTRA_FLAGS) $(WARN_FLAGS) -g
 @NATIVE_TRUE@mtest_LDADD = libbacktrace.la
 @HAVE_ELF_TRUE@xztest_SOURCES = xztest.c testlib.c
 @HAVE_ELF_TRUE@xztest_CFLAGS = $(libbacktrace_TEST_CFLAGS) -DSRCDIR=\"$(srcdir)\"
-@HAVE_ELF_TRUE@xztest_LDADD = libbacktrace.la $(am__append_26) \
+@HAVE_ELF_TRUE@xztest_LDADD = libbacktrace.la $(am__append_27) \
 @HAVE_ELF_TRUE@	$(CLOCK_GETTIME_LINK)
 @HAVE_ELF_TRUE@xztest_alloc_SOURCES = $(xztest_SOURCES)
 @HAVE_ELF_TRUE@xztest_alloc_CFLAGS = $(xztest_CFLAGS)
 @HAVE_ELF_TRUE@xztest_alloc_LDADD = libbacktrace_alloc.la \
-@HAVE_ELF_TRUE@	$(am__append_27) $(CLOCK_GETTIME_LINK)
+@HAVE_ELF_TRUE@	$(am__append_28) $(CLOCK_GETTIME_LINK)
 CLEANFILES = \
 	$(TESTS) *.debug elf_for_test.c edtest2_build.c gen_edtest2_build \
 	*.dsyms *.fsyms *.keepsyms *.dbg *.mdbg *.mdbg.xz *.strip
@@ -2392,8 +2396,8 @@ uninstall-am:
 .PRECIOUS: Makefile
 
 
-@HAVE_DSYMUTIL_TRUE@%.dSYM: %
-@HAVE_DSYMUTIL_TRUE@	$(DSYMUTIL) $<
+@USE_DSYMUTIL_TRUE@%.dSYM: %
+@USE_DSYMUTIL_TRUE@	$(DSYMUTIL) $<
 
 @HAVE_ELF_TRUE@@HAVE_OBJCOPY_DEBUGLINK_TRUE@@NATIVE_TRUE@elf_for_test.c: elf.c
 @HAVE_ELF_TRUE@@HAVE_OBJCOPY_DEBUGLINK_TRUE@@NATIVE_TRUE@	SEARCH='^#define SYSTEM_BUILD_ID_DIR.*$$'; \
diff --git a/libbacktrace/configure b/libbacktrace/configure
index 031a156..8c8c34d 100755
--- a/libbacktrace/configure
+++ b/libbacktrace/configure
@@ -645,8 +645,8 @@ COMM
 HAVE_XZ_FALSE
 HAVE_XZ_TRUE
 XZ
-HAVE_DSYMUTIL_FALSE
-HAVE_DSYMUTIL_TRUE
+USE_DSYMUTIL_FALSE
+USE_DSYMUTIL_TRUE
 HAVE_OBJCOPY_DEBUGLINK_FALSE
 HAVE_OBJCOPY_DEBUGLINK_TRUE
 READELF
@@ -13860,12 +13860,12 @@ $as_echo "no" >&6; }
 fi
 
 
- if test -n "${DSYMUTIL}"; then
-  HAVE_DSYMUTIL_TRUE=
-  HAVE_DSYMUTIL_FALSE='#'
+ if test -n "${DSYMUTIL}" -a "$FORMAT_FILE" = "macho.lo"; then
+  USE_DSYMUTIL_TRUE=
+  USE_DSYMUTIL_FALSE='#'
 else
-  HAVE_DSYMUTIL_TRUE='#'
-  HAVE_DSYMUTIL_FALSE=
+  USE_DSYMUTIL_TRUE='#'
+  USE_DSYMUTIL_FALSE=
 fi
 
 
@@ -14271,8 +14271,8 @@ if test -z "${HAVE_OBJCOPY_DEBUGLINK_TRUE}" && test -z "${HAVE_OBJCOPY_DEBUGLINK
   as_fn_error $? "conditional \"HAVE_OBJCOPY_DEBUGLINK\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
-if test -z "${HAVE_DSYMUTIL_TRUE}" && test -z "${HAVE_DSYMUTIL_FALSE}"; then
-  as_fn_error $? "conditional \"HAVE_DSYMUTIL\" was never defined.
+if test -z "${USE_DSYMUTIL_TRUE}" && test -z "${USE_DSYMUTIL_FALSE}"; then
+  as_fn_error $? "conditional \"USE_DSYMUTIL\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
 if test -z "${HAVE_XZ_TRUE}" && test -z "${HAVE_XZ_FALSE}"; then
diff --git a/libbacktrace/configure.ac b/libbacktrace/configure.ac
index 0659ea6..ec456bf 100644
--- a/libbacktrace/configure.ac
+++ b/libbacktrace/configure.ac
@@ -510,7 +510,7 @@ AM_CONDITIONAL(HAVE_OBJCOPY_DEBUGLINK, test "$libbacktrace_cv_objcopy_debuglink"
 
 AC_ARG_VAR(DSYMUTIL, [location of dsymutil])
 AC_CHECK_PROG(DSYMUTIL, dsymutil, dsymutil)
-AM_CONDITIONAL(HAVE_DSYMUTIL, test -n "${DSYMUTIL}")
+AM_CONDITIONAL(USE_DSYMUTIL, test -n "${DSYMUTIL}" -a "$FORMAT_FILE" = "macho.lo")
 
 AC_ARG_VAR(NM, [location of nm])
 AC_CHECK_PROG(NM, nm, nm)
diff --git a/libbacktrace/dwarf.c b/libbacktrace/dwarf.c
index 386701b..582f34b 100644
--- a/libbacktrace/dwarf.c
+++ b/libbacktrace/dwarf.c
@@ -3558,6 +3558,11 @@ report_inlined_functions (uintptr_t pc, struct function *function,
   if (function->function_addrs_count == 0)
     return 0;
 
+  /* Our search isn't safe if pc == -1, as that is the sentinel
+     value.  */
+  if (pc + 1 == 0)
+    return 0;
+
   p = ((struct function_addrs *)
        bsearch (&pc, function->function_addrs,
 		function->function_addrs_count,
@@ -3567,9 +3572,12 @@ report_inlined_functions (uintptr_t pc, struct function *function,
     return 0;
 
   /* Here pc >= p->low && pc < (p + 1)->low.  The function_addrs are
-     sorted by low, so we are at the end of a range of function_addrs
-     with the same low alue.  Walk backward and use the first range
-     that includes pc.  */
+     sorted by low, so if pc > p->low we are at the end of a range of
+     function_addrs with the same low value.  If pc == p->low walk
+     forward to the end of the range with that low value.  Then walk
+     backward and use the first range that includes pc.  */
+  while (pc == (p + 1)->low)
+    ++p;
   match = NULL;
   while (1)
     {
@@ -3636,8 +3644,10 @@ dwarf_lookup_pc (struct backtrace_state *state, struct dwarf_data *ddata,
 
   *found = 1;
 
-  /* Find an address range that includes PC.  */
-  entry = (ddata->addrs_count == 0
+  /* Find an address range that includes PC.  Our search isn't safe if
+     PC == -1, as we use that as a sentinel value, so skip the search
+     in that case.  */
+  entry = (ddata->addrs_count == 0 || pc + 1 == 0
 	   ? NULL
 	   : bsearch (&pc, ddata->addrs, ddata->addrs_count,
 		      sizeof (struct unit_addrs), unit_addrs_search));
@@ -3649,9 +3659,12 @@ dwarf_lookup_pc (struct backtrace_state *state, struct dwarf_data *ddata,
     }
 
   /* Here pc >= entry->low && pc < (entry + 1)->low.  The unit_addrs
-     are sorted by low, so we are at the end of a range of unit_addrs
-     with the same low value.  Walk backward and use the first range
-     that includes pc.  */
+     are sorted by low, so if pc > p->low we are at the end of a range
+     of unit_addrs with the same low value.  If pc == p->low walk
+     forward to the end of the range with that low value.  Then walk
+     backward and use the first range that includes pc.  */
+  while (pc == (entry + 1)->low)
+    ++entry;
   found_entry = 0;
   while (1)
     {
@@ -3832,9 +3845,12 @@ dwarf_lookup_pc (struct backtrace_state *state, struct dwarf_data *ddata,
     return callback (data, pc, ln->filename, ln->lineno, NULL);
 
   /* Here pc >= p->low && pc < (p + 1)->low.  The function_addrs are
-     sorted by low, so we are at the end of a range of function_addrs
-     with the same low alue.  Walk backward and use the first range
-     that includes pc.  */
+     sorted by low, so if pc > p->low we are at the end of a range of
+     function_addrs with the same low value.  If pc == p->low walk
+     forward to the end of the range with that low value.  Then walk
+     backward and use the first range that includes pc.  */
+  while (pc == (p + 1)->low)
+    ++p;
   fmatch = NULL;
   while (1)
     {
diff --git a/libbacktrace/elf.c b/libbacktrace/elf.c
index 941f820d..d52b86c 100644
--- a/libbacktrace/elf.c
+++ b/libbacktrace/elf.c
@@ -2081,10 +2081,10 @@ elf_zlib_inflate (const unsigned char *pin, size_t sin, uint16_t *zdebug_table,
 			{
 			case 6:
 			  *plen++ = prev;
-			  /* fallthrough */
+			  ATTRIBUTE_FALLTHROUGH;
 			case 5:
 			  *plen++ = prev;
-			  /* fallthrough */
+			  ATTRIBUTE_FALLTHROUGH;
 			case 4:
 			  *plen++ = prev;
 			}
@@ -2115,22 +2115,22 @@ elf_zlib_inflate (const unsigned char *pin, size_t sin, uint16_t *zdebug_table,
 			{
 			case 10:
 			  *plen++ = 0;
-			  /* fallthrough */
+			  ATTRIBUTE_FALLTHROUGH;
 			case 9:
 			  *plen++ = 0;
-			  /* fallthrough */
+			  ATTRIBUTE_FALLTHROUGH;
 			case 8:
 			  *plen++ = 0;
-			  /* fallthrough */
+			  ATTRIBUTE_FALLTHROUGH;
 			case 7:
 			  *plen++ = 0;
-			  /* fallthrough */
+			  ATTRIBUTE_FALLTHROUGH;
 			case 6:
 			  *plen++ = 0;
-			  /* fallthrough */
+			  ATTRIBUTE_FALLTHROUGH;
 			case 5:
 			  *plen++ = 0;
-			  /* fallthrough */
+			  ATTRIBUTE_FALLTHROUGH;
 			case 4:
 			  *plen++ = 0;
 			}
diff --git a/libbacktrace/internal.h b/libbacktrace/internal.h
index 047a700..659db9e 100644
--- a/libbacktrace/internal.h
+++ b/libbacktrace/internal.h
@@ -56,6 +56,14 @@ POSSIBILITY OF SUCH DAMAGE.  */
 # endif
 #endif
 
+#ifndef ATTRIBUTE_FALLTHROUGH
+# if (GCC_VERSION >= 7000)
+#  define ATTRIBUTE_FALLTHROUGH __attribute__ ((__fallthrough__))
+# else
+#  define ATTRIBUTE_FALLTHROUGH
+# endif
+#endif
+
 #ifndef HAVE_SYNC_FUNCTIONS
 
 /* Define out the sync functions.  These should never be called if