Merge with gnulib, pacifying GCC 7

This incorporates:
2017-05-16 manywarnings: update for GCC 7
2017-05-15 sys_select: Avoid "was expanded before it was required"
* configure.ac (nw): Suppress GCC 7’s new -Wduplicated-branches and
-Wformat-overflow=2 options, due to too many false alarms.
* doc/misc/texinfo.tex, lib/strftime.c, m4/manywarnings.m4:
Copy from gnulib.
* m4/gnulib-comp.m4: Regenerate.
* src/coding.c (decode_coding_iso_2022):
Fix bug uncovered by -Wimplicit-fallthrough.
* src/conf_post.h (FALLTHROUGH): New macro.
Use it to mark all switch cases that fall through.
* src/editfns.c (styled_format): Use !, not ~, on bool.
* src/gtkutil.c (xg_check_special_colors):
When using sprintf, don’t trust Gtk to output colors in [0, 1] range.
(xg_update_scrollbar_pos): Avoid use of possibly-uninitialized bool;
this bug was actually caught by Clang.
* src/search.c (boyer_moore):
Tell GCC that CHAR_BASE, if nonzero, must be a non-ASCII character.
* src/xterm.c (x_draw_glyphless_glyph_string_foreground):
Tell GCC that glyph->u.glyphless.ch must be a character.

25 files changed, 118 insertions, 70 deletions

diff --git a/configure.ac b/configure.ac
index d085552ffea..34b75a768bf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -921,6 +921,8 @@ AS_IF([test $gl_gcc_warnings = no],
     [gl_WARN_ADD([-Werror], [WERROR_CFLAGS])])
   AC_SUBST([WERROR_CFLAGS])
 
+  nw="$nw -Wduplicated-branches"    # Too many false alarms
+  nw="$nw -Wformat-overflow=2"      # False alarms due to GCC bug 80776
   nw="$nw -Wsystem-headers"         # Don't let system headers trigger warnings
   nw="$nw -Woverlength-strings"     # Not a problem these days
   nw="$nw -Wformat-nonliteral"      # we do this a lot
diff --git a/doc/misc/texinfo.tex b/doc/misc/texinfo.tex
index 9cd73101c1f..8204f3e3aeb 100644
--- a/doc/misc/texinfo.tex
+++ b/doc/misc/texinfo.tex
@@ -3,7 +3,7 @@
 % Load plain if necessary, i.e., if running under initex.
 \expandafter\ifx\csname fmtname\endcsname\relax\input plain\fi
 %
-\def\texinfoversion{2017-04-14.11}
+\def\texinfoversion{2017-05-14.14}
 %
 % Copyright 1985, 1986, 1988, 1990, 1991, 1992, 1993, 1994, 1995,
 % 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
@@ -9118,7 +9118,13 @@ end
     \xdef\safexrefname{#1}%
   }%
   %
-  \expandafter\gdef\csname XR\safexrefname\endcsname{#2}% remember this xref
+  \bgroup
+    \expandafter\gdef\csname XR\safexrefname\endcsname{#2}%
+  \egroup
+  % We put the \gdef inside a group to avoid the definitions building up on 
+  % TeX's save stack, which can cause it to run out of space for aux files with 
+  % thousands of lines.  \gdef doesn't use the save stack, but \csname does
+  % when it defines an unknown control sequence as \relax. 
   %
   % Was that xref control sequence that we just defined for a float?
   \expandafter\iffloat\csname XR\safexrefname\endcsname
diff --git a/lib-src/ebrowse.c b/lib-src/ebrowse.c
index 623911027ce..51d181997b1 100644
--- a/lib-src/ebrowse.c
+++ b/lib-src/ebrowse.c
@@ -3059,8 +3059,7 @@ class_definition (struct sym *containing, int tag, int flags, int nested)
                  MATCH until we see something like `;' or `{'.  */
               while (!LOOKING_AT3 (';', YYEOF, '{'))
                 MATCH ();
-	      done = 1;
-
+	      FALLTHROUGH;
             case '{':
               done = 1;
 	      break;
@@ -3184,7 +3183,7 @@ declaration (int flags)
 	      free (id);
 	      return;
 	    }
-
+	  FALLTHROUGH;
         case '=':
           /* Assumed to be the start of an initialization in this
 	     context.  */
diff --git a/lib-src/etags.c b/lib-src/etags.c
index 015cbbe0ef3..6f280d8ab40 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -1157,7 +1157,7 @@ main (int argc, char **argv)
       case 'c':
 	/* Backward compatibility: support obsolete --ignore-case-regexp. */
 	optarg = concat (optarg, "i", ""); /* memory leak here */
-	/* FALLTHRU */
+	FALLTHROUGH;
       case 'r':
 	argbuffer[current_arg].arg_type = at_regexp;
 	argbuffer[current_arg].what = optarg;
@@ -1192,7 +1192,7 @@ main (int argc, char **argv)
       case 't': typedefs = true;				break;
       case 'T': typedefs = typedefs_or_cplusplus = true;	break;
       case 'u': update = true;					break;
-      case 'v': vgrind_style = true;			  /*FALLTHRU*/
+      case 'v': vgrind_style = true;				FALLTHROUGH;
       case 'x': cxref_style = true;				break;
       case 'w': no_warnings = true;				break;
       default:
@@ -2564,7 +2564,7 @@ hash (const char *str, int len)
     {
       default:
         hval += asso_values[(unsigned char) str[2]];
-      /*FALLTHROUGH*/
+	FALLTHROUGH;
       case 2:
         hval += asso_values[(unsigned char) str[1]];
         break;
@@ -3013,7 +3013,7 @@ consider_token (char *str, int len, int c, int *c_extp,
 	 *c_extp = (*c_extp | C_PLPL) & ~C_AUTO;
        if (toktype == st_C_template)
 	 break;
-       /* FALLTHRU */
+       FALLTHROUGH;
      case st_C_struct:
      case st_C_enum:
        if (parlev == 0
@@ -3176,7 +3176,7 @@ consider_token (char *str, int len, int c, int *c_extp,
 	     default:
 	       break;
 	     }
-	  /* FALLTHRU */
+	   FALLTHROUGH;
 	  case fvnameseen:
 	  if (len >= 10 && strneq (str+len-10, "::operator", 10))
 	    {
@@ -3387,7 +3387,7 @@ C_entries (int c_ext, FILE *inf)
 	    case '\0':
 	      /* Hmmm, something went wrong. */
 	      CNL ();
-	      /* FALLTHRU */
+	      FALLTHROUGH;
 	    case '\'':
 	      inchar = false;
 	      break;
@@ -3828,7 +3828,7 @@ C_entries (int c_ext, FILE *inf)
 		      || (members
 			  && plainc && instruct))
 		    make_C_tag (true);  /* a function */
-		  /* FALLTHRU */
+		  FALLTHROUGH;
 		default:
 		  fvextern = false;
 		  fvdef = fvnone;
@@ -3838,7 +3838,7 @@ C_entries (int c_ext, FILE *inf)
 		  else
 		    token.valid = false;
 		} /* switch (fvdef) */
-	      /* FALLTHRU */
+	      FALLTHROUGH;
 	    default:
 	      if (!instruct)
 		typdef = tnone;
@@ -3926,7 +3926,7 @@ C_entries (int c_ext, FILE *inf)
 		      || (globals && bracelev == 0
 			  && (!fvextern || declarations)))
 		    make_C_tag (false); /* a variable */
-		  /* FALLTHRU */
+		  FALLTHROUGH;
 		default:
 		  fvdef = fvnone;
 		}
@@ -3959,7 +3959,7 @@ C_entries (int c_ext, FILE *inf)
 		  fvdef = fignore;
 		  break;
 		}
-	      /* FALLTHRU */
+	      FALLTHROUGH;
 	    case foperator:
 	      fvdef = fstartlist;
 	      break;
@@ -4049,7 +4049,7 @@ C_entries (int c_ext, FILE *inf)
 		    }
 		}
 	      make_C_tag (true);    /* a function */
-	      /* FALLTHRU */
+	      FALLTHROUGH;
 	    case fignore:
 	      fvdef = fvnone;
 	      break;
@@ -4142,7 +4142,7 @@ C_entries (int c_ext, FILE *inf)
 	      if ((members && bracelev == 1)
 		  || (globals && bracelev == 0 && (!fvextern || declarations)))
 		make_C_tag (false); /* a variable */
-	      /* FALLTHRU */
+	      FALLTHROUGH;
 	    default:
 	      fvdef = vignore;
 	    }
@@ -4169,7 +4169,7 @@ C_entries (int c_ext, FILE *inf)
 	      objdef = omethodsign;
 	      break;
 	    }
-	  /* FALLTHRU */
+	  FALLTHROUGH;
 	resetfvdef:
 	case '#': case '~': case '&': case '%': case '/':
 	case '|': case '^': case '!': case '.': case '?':
@@ -6354,7 +6354,7 @@ add_regex (char *regexp_pattern, language *lang)
 	break;
       case 's':
 	single_line = true;
-	/* FALLTHRU */
+	FALLTHROUGH;
       case 'm':
 	multi_line = true;
 	need_filebuf = true;
diff --git a/lib/strftime.c b/lib/strftime.c
index e4d78ef7011..99bee4ef978 100644
--- a/lib/strftime.c
+++ b/lib/strftime.c
@@ -68,6 +68,14 @@ extern char *tzname[];
 #include <string.h>
 #include <stdbool.h>
 
+#ifndef FALLTHROUGH
+# if __GNUC__ < 7
+#  define FALLTHROUGH ((void) 0)
+# else
+#  define FALLTHROUGH __attribute__ ((__fallthrough__))
+# endif
+#endif
+
 #ifdef COMPILE_WIDE
 # include <endian.h>
 # define CHAR_T wchar_t
@@ -1138,8 +1146,7 @@ __strftime_internal (STREAM_OR_CHAR_T *s, STRFTIME_ARG (size_t maxsize)
 #ifndef _NL_CURRENT
           format_char = L_('p');
 #endif
-          /* FALLTHROUGH */
-
+          FALLTHROUGH;
         case L_('p'):
           if (change_case)
             {
@@ -1474,7 +1481,7 @@ __strftime_internal (STREAM_OR_CHAR_T *s, STRFTIME_ARG (size_t maxsize)
 
         case L_('\0'):          /* GNU extension: % at end of format.  */
             --f;
-            /* Fall through.  */
+            FALLTHROUGH;
         default:
           /* Unknown format; output the format, including the '%',
              since this is most likely the right thing to do if a
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 8295e483582..3f196d4f1de 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -375,7 +375,7 @@ AC_DEFUN([gl_INIT],
     AC_LIBOBJ([symlink])
   fi
   gl_UNISTD_MODULE_INDICATOR([symlink])
-  gl_HEADER_SYS_SELECT
+  AC_REQUIRE([gl_HEADER_SYS_SELECT])
   AC_PROG_MKDIR_P
   gl_HEADER_SYS_STAT_H
   AC_PROG_MKDIR_P
diff --git a/m4/manywarnings.m4 b/m4/manywarnings.m4
index 0f06adecfbb..2d35eff6a2c 100644
--- a/m4/manywarnings.m4
+++ b/m4/manywarnings.m4
@@ -99,12 +99,11 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
   # comm -3 \
   #  <(sed -n 's/^  *\(-[^ ]*\) .*/\1/p' manywarnings.m4 | sort) \
   #  <(gcc --help=warnings | sed -n 's/^  \(-[^ ]*\) .*/\1/p' | sort |
-  #      grep -v -x -f <(
+  #      grep -v -x -F -f <(
   #         awk '/^[^#]/ {print $1}' ../build-aux/gcc-warning.spec))
 
   gl_manywarn_set=
-  for gl_manywarn_item in \
-    -fno-common \
+  for gl_manywarn_item in -fno-common \
     -W \
     -Wabi \
     -Waddress \
@@ -113,6 +112,8 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
     -Wattributes \
     -Wbad-function-cast \
     -Wbool-compare \
+    -Wbool-operation \
+    -Wbuiltin-declaration-mismatch \
     -Wbuiltin-macro-redefined \
     -Wcast-align \
     -Wchar-subscripts \
@@ -122,6 +123,7 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
     -Wcomments \
     -Wcoverage-mismatch \
     -Wcpp \
+    -Wdangling-else \
     -Wdate-time \
     -Wdeprecated \
     -Wdeprecated-declarations \
@@ -131,10 +133,13 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
     -Wdiscarded-qualifiers \
     -Wdiv-by-zero \
     -Wdouble-promotion \
+    -Wduplicated-branches \
     -Wduplicated-cond \
+    -Wduplicate-decl-specifier \
     -Wempty-body \
     -Wendif-labels \
     -Wenum-compare \
+    -Wexpansion-to-defined \
     -Wextra \
     -Wformat-contains-nul \
     -Wformat-extra-args \
@@ -155,6 +160,7 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
     -Winit-self \
     -Winline \
     -Wint-conversion \
+    -Wint-in-bool-context \
     -Wint-to-pointer-cast \
     -Winvalid-memory-model \
     -Winvalid-pch \
@@ -163,6 +169,7 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
     -Wlogical-op \
     -Wmain \
     -Wmaybe-uninitialized \
+    -Wmemset-elt-size \
     -Wmemset-transposed-args \
     -Wmisleading-indentation \
     -Wmissing-braces \
@@ -188,9 +195,12 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
     -Wpacked-bitfield-compat \
     -Wparentheses \
     -Wpointer-arith \
+    -Wpointer-compare \
     -Wpointer-sign \
     -Wpointer-to-int-cast \
     -Wpragmas \
+    -Wpsabi \
+    -Wrestrict \
     -Wreturn-local-addr \
     -Wreturn-type \
     -Wscalar-storage-order \
@@ -214,6 +224,7 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
     -Wswitch \
     -Wswitch-bool \
     -Wswitch-default \
+    -Wswitch-unreachable \
     -Wsync-nand \
     -Wsystem-headers \
     -Wtautological-compare \
@@ -247,10 +258,18 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
 
   # gcc --help=warnings outputs an unusual form for these options; list
   # them here so that the above 'comm' command doesn't report a false match.
+  # Would prefer "min (PTRDIFF_MAX, SIZE_MAX)", but it must be a literal:
+  ptrdiff_max_max=9223372036854775807
+  gl_manywarn_set="$gl_manywarn_set -Walloc-size-larger-than=$ptrdiff_max_max"
   gl_manywarn_set="$gl_manywarn_set -Warray-bounds=2"
+  gl_manywarn_set="$gl_manywarn_set -Wformat-overflow=2"
+  gl_manywarn_set="$gl_manywarn_set -Wformat-truncation=2"
+  gl_manywarn_set="$gl_manywarn_set -Wimplicit-fallthrough=5"
   gl_manywarn_set="$gl_manywarn_set -Wnormalized=nfc"
   gl_manywarn_set="$gl_manywarn_set -Wshift-overflow=2"
+  gl_manywarn_set="$gl_manywarn_set -Wstringop-overflow=2"
   gl_manywarn_set="$gl_manywarn_set -Wunused-const-variable=2"
+  gl_manywarn_set="$gl_manywarn_set -Wvla-larger-than=4031"
 
   # These are needed for older GCC versions.
   if test -n "$GCC"; then
diff --git a/src/bidi.c b/src/bidi.c
index b75ad933626..dce0bf695f6 100644
--- a/src/bidi.c
+++ b/src/bidi.c
@@ -2092,7 +2092,7 @@ bidi_resolve_explicit (struct bidi_it *bidi_it)
 	  type = RLI;
 	  bidi_it->orig_type = type;
 	}
-      /* FALLTHROUGH */
+      FALLTHROUGH;
     case RLI:	/* X5a */
       if (override == NEUTRAL_DIR)
 	bidi_it->type_after_wn = type;
diff --git a/src/callint.c b/src/callint.c
index d96454883cf..96436116c8b 100644
--- a/src/callint.c
+++ b/src/callint.c
@@ -690,6 +690,7 @@ invoke it.  If KEYS is omitted or nil, the return value of
 	case 'N':     /* Prefix arg as number, else number from minibuffer.  */
 	  if (!NILP (prefix_arg))
 	    goto have_prefix_arg;
+	  FALLTHROUGH;
 	case 'n':		/* Read number from minibuffer.  */
 	  args[i] = call1 (Qread_number, callint_message);
 	  /* Passing args[i] directly stimulates compiler bug.  */
diff --git a/src/ccl.c b/src/ccl.c
index 90bd2f46794..b2caf413f7a 100644
--- a/src/ccl.c
+++ b/src/ccl.c
@@ -1000,7 +1000,7 @@ ccl_driver (struct ccl_program *ccl, int *source, int *destination, int src_size
 
 	case CCL_ReadBranch:	/* CCCCCCCCCCCCCCCCCCCCrrrXXXXX */
 	  CCL_READ_CHAR (reg[rrr]);
-	  /* fall through ... */
+	  FALLTHROUGH;
 	case CCL_Branch:	/* CCCCCCCCCCCCCCCCCCCCrrrXXXXX */
 	{
 	  int ioff = 0 <= reg[rrr] && reg[rrr] < field1 ? reg[rrr] : field1;
@@ -1174,6 +1174,7 @@ ccl_driver (struct ccl_program *ccl, int *source, int *destination, int src_size
 
 	case CCL_ReadJumpCondExprConst: /* A--D--D--R--E--S--S-rrrXXXXX */
 	  CCL_READ_CHAR (reg[rrr]);
+	  FALLTHROUGH;
 	case CCL_JumpCondExprConst: /* A--D--D--R--E--S--S-rrrXXXXX */
 	  i = reg[rrr];
 	  jump_address = ic + ADDR;
@@ -1184,6 +1185,7 @@ ccl_driver (struct ccl_program *ccl, int *source, int *destination, int src_size
 
 	case CCL_ReadJumpCondExprReg: /* A--D--D--R--E--S--S-rrrXXXXX */
 	  CCL_READ_CHAR (reg[rrr]);
+	  FALLTHROUGH;
 	case CCL_JumpCondExprReg:
 	  i = reg[rrr];
 	  jump_address = ic + ADDR;
diff --git a/src/coding.c b/src/coding.c
index 367a9759848..5682fc015ad 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -3611,7 +3611,7 @@ decode_coding_iso_2022 (struct coding_system *coding)
 	      || CODING_ISO_FLAGS (coding) & CODING_ISO_FLAG_SEVEN_BITS)
 	    goto invalid_code;
 	  /* This is a graphic character, we fall down ... */
-
+	  FALLTHROUGH;
 	case ISO_graphic_plane_1:
 	  if (charset_id_1 < 0)
 	    goto invalid_code;
@@ -3646,6 +3646,7 @@ decode_coding_iso_2022 (struct coding_system *coding)
 	case ISO_single_shift_2_7:
 	  if (! (CODING_ISO_FLAGS (coding) & CODING_ISO_FLAG_SEVEN_BITS))
 	    goto invalid_code;
+	  FALLTHROUGH;
 	case ISO_single_shift_2:
 	  if (! (CODING_ISO_FLAGS (coding) & CODING_ISO_FLAG_SINGLE_SHIFT))
 	    goto invalid_code;
@@ -3797,6 +3798,7 @@ decode_coding_iso_2022 (struct coding_system *coding)
 		{
 		case ']':	/* end of the current direction */
 		  coding->mode &= ~CODING_MODE_DIRECTION;
+		  break;
 
 		case '0':	/* end of the current direction */
 		case '1':	/* start of left-to-right direction */
diff --git a/src/conf_post.h b/src/conf_post.h
index 95ebd5511ca..4fc0428df5a 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -244,6 +244,12 @@ extern int emacs_setenv_TZ (char const *);
 # define ATTRIBUTE_FORMAT(spec) /* empty */
 #endif
 
+#if GNUC_PREREQ (7, 0, 0)
+# define FALLTHROUGH __attribute__ ((__fallthrough__))
+#else
+# define FALLTHROUGH ((void) 0)
+#endif
+
 #if GNUC_PREREQ (4, 4, 0) && defined __GLIBC_MINOR__
 # define PRINTF_ARCHETYPE __gnu_printf__
 #elif GNUC_PREREQ (4, 4, 0) && defined __MINGW32__
diff --git a/src/data.c b/src/data.c
index 44f7ba0e881..3ff2a809744 100644
--- a/src/data.c
+++ b/src/data.c
@@ -2153,7 +2153,7 @@ If the current binding is global (the default), the value is nil.  */)
 	else if (!BUFFER_OBJFWDP (valcontents))
 	  return Qnil;
       }
-      /* FALLTHROUGH */
+      FALLTHROUGH;
     case SYMBOL_LOCALIZED:
       /* For a local variable, record both the symbol and which
 	 buffer's or frame's value we are saving.  */
diff --git a/src/doprnt.c b/src/doprnt.c
index 09051adc053..bed9350f4a6 100644
--- a/src/doprnt.c
+++ b/src/doprnt.c
@@ -352,6 +352,7 @@ doprnt (char *buffer, ptrdiff_t bufsize, const char *format,
 
 	    case 'S':
 	      string[-1] = 's';
+	      FALLTHROUGH;
 	    case 's':
 	      if (fmtcpy[1] != 's')
 		minlen = atoi (&fmtcpy[1]);
diff --git a/src/editfns.c b/src/editfns.c
index 38530437a2f..ecb8e3f0838 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -1595,10 +1595,10 @@ time_arith (Lisp_Object a, Lisp_Object b,
     {
     default:
       val = Fcons (make_number (t.ps), val);
-      /* Fall through.  */
+      FALLTHROUGH;
     case 3:
       val = Fcons (make_number (t.us), val);
-      /* Fall through.  */
+      FALLTHROUGH;
     case 2:
       val = Fcons (make_number (t.lo), val);
       val = Fcons (make_number (t.hi), val);
@@ -4072,8 +4072,8 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
 	    }
 
 	  /* Ignore flags when sprintf ignores them.  */
-	  space_flag &= ~ plus_flag;
-	  zero_flag &= ~ minus_flag;
+	  space_flag &= ! plus_flag;
+	  zero_flag &= ! minus_flag;
 
 	  char *num_end;
 	  uintmax_t raw_field_width = strtoumax (format, &num_end, 10);
@@ -4311,7 +4311,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
 		  {
 		    memcpy (f, pMd, pMlen);
 		    f += pMlen;
-		    zero_flag &= ~ precision_given;
+		    zero_flag &= ! precision_given;
 		  }
 		*f++ = conversion;
 		*f = '\0';
diff --git a/src/eval.c b/src/eval.c
index 848955c2794..98d25cc4fed 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3212,7 +3212,7 @@ do_specbind (struct Lisp_Symbol *sym, union specbinding *bind,
           set_default_internal (specpdl_symbol (bind), value, bindflag);
 	  return;
 	}
-      /* FALLTHROUGH */
+      FALLTHROUGH;
     case SYMBOL_LOCALIZED:
       set_internal (specpdl_symbol (bind), value, Qnil, bindflag);
       break;
@@ -3390,12 +3390,10 @@ do_one_unbind (union specbinding *this_binding, bool unwinding,
                             Qnil, bindflag);
 	    break;
 	  }
-	else
-	  { /* FALLTHROUGH!!
-	       NOTE: we only ever come here if make_local_foo was used for
-	       the first time on this var within this let.  */
-	  }
       }
+      /* Come here only if make_local_foo was used for the first time
+	 on this var within this let.  */
+      FALLTHROUGH;
     case SPECPDL_LET_DEFAULT:
       set_default_internal (specpdl_symbol (this_binding),
                             specpdl_old_value (this_binding),
@@ -3676,12 +3674,10 @@ backtrace_eval_unrewind (int distance)
 		SET_SYMBOL_VAL (XSYMBOL (sym), old_value);
 		break;
 	      }
-	    else
-	      { /* FALLTHROUGH!!
-		   NOTE: we only ever come here if make_local_foo was used for
-		   the first time on this var within this let.  */
-	      }
 	  }
+	  /* Come here only if make_local_foo was used for the first
+	     time on this var within this let.  */
+	  FALLTHROUGH;
 	case SPECPDL_LET_DEFAULT:
 	  {
 	    Lisp_Object sym = specpdl_symbol (tmp);
@@ -3837,7 +3833,7 @@ mark_specpdl (union specbinding *first, union specbinding *ptr)
 	case SPECPDL_LET_DEFAULT:
 	case SPECPDL_LET_LOCAL:
 	  mark_object (specpdl_where (pdl));
-	  /* Fall through.  */
+	  FALLTHROUGH;
 	case SPECPDL_LET:
 	  mark_object (specpdl_symbol (pdl));
 	  mark_object (specpdl_old_value (pdl));
diff --git a/src/filelock.c b/src/filelock.c
index 67e8dbd34ed..bfa1d63d833 100644
--- a/src/filelock.c
+++ b/src/filelock.c
@@ -569,7 +569,7 @@ current_lock_owner (lock_info_type *owner, char *lfname)
       if (! (boot[0] == '\200' && boot[1] == '\242'))
 	return -1;
       boot += 2;
-      /* Fall through.  */
+      FALLTHROUGH;
     case ':':
       if (! c_isdigit (boot[0]))
 	return -1;
diff --git a/src/gnutls.c b/src/gnutls.c
index 28ab10de05c..2078ad88f28 100644
--- a/src/gnutls.c
+++ b/src/gnutls.c
@@ -605,6 +605,7 @@ emacs_gnutls_handle_error (gnutls_session_t session, int err)
                        max_log_level,
                        "retry:",
                        str);
+	  FALLTHROUGH;
         default:
           GNUTLS_LOG2 (1,
                        max_log_level,
diff --git a/src/gtkutil.c b/src/gtkutil.c
index 1b63293fe55..16eb284d7c7 100644
--- a/src/gtkutil.c
+++ b/src/gtkutil.c
@@ -554,10 +554,11 @@ xg_check_special_colors (struct frame *f,
     else
       gtk_style_context_get_background_color (gsty, state, &col);
 
-    sprintf (buf, "rgb:%04x/%04x/%04x",
-             (unsigned) (col.red * 65535),
-             (unsigned) (col.green * 65535),
-             (unsigned) (col.blue * 65535));
+    unsigned short
+      r = col.red * 65535,
+      g = col.green * 65535,
+      b = col.blue * 65535;
+    sprintf (buf, "rgb:%04x/%04x/%04x", r, g, b);
     success_p = x_parse_color (f, buf, color) != 0;
 #else
     GtkStyle *gsty = gtk_widget_get_style (FRAME_GTK_WIDGET (f));
@@ -3856,7 +3857,6 @@ xg_update_scrollbar_pos (struct frame *f,
       GtkWidget *wparent = gtk_widget_get_parent (wscroll);
       gint msl;
       int scale = xg_get_gdk_scale ();
-      bool hidden;
 
       top /= scale;
       left /= scale;
@@ -3875,13 +3875,13 @@ xg_update_scrollbar_pos (struct frame *f,
       /* Move and resize to new values.  */
       gtk_fixed_move (GTK_FIXED (wfixed), wparent, left, top);
       gtk_widget_style_get (wscroll, "min-slider-length", &msl, NULL);
-      if (msl > height)
+      bool hidden = height < msl;
+      if (hidden)
         {
           /* No room.  Hide scroll bar as some themes output a warning if
              the height is less than the min size.  */
           gtk_widget_hide (wparent);
           gtk_widget_hide (wscroll);
-	  hidden = true;
         }
       else
         {
diff --git a/src/indent.c b/src/indent.c
index f630ebb847c..adecc3622a8 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -925,6 +925,7 @@ position_indentation (ptrdiff_t pos_byte)
 	case 0240:
 	  if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
 	    return column;
+	  FALLTHROUGH;
 	case ' ':
 	  column++;
 	  break;
diff --git a/src/lread.c b/src/lread.c
index c03aad4f722..5e737d690c6 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -2309,6 +2309,7 @@ read_escape (Lisp_Object readcharfun, bool stringp)
       c = READCHAR;
       if (c != '-')
 	error ("Invalid escape character syntax");
+      FALLTHROUGH;
     case '^':
       c = READCHAR;
       if (c == '\\')
@@ -2399,6 +2400,7 @@ read_escape (Lisp_Object readcharfun, bool stringp)
     case 'U':
       /* Post-Unicode-2.0: Up to eight hex chars.  */
       unicode_hex_count = 8;
+      FALLTHROUGH;
     case 'u':
 
       /* A Unicode escape.  We only permit them in strings and characters,
@@ -3278,11 +3280,11 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	    *pch = c;
 	    return Qnil;
 	  }
-
-	/* Otherwise, we fall through!  Note that the atom-reading loop
-	   below will now loop at least once, assuring that we will not
-	   try to UNREAD two characters in a row.  */
       }
+      /* The atom-reading loop below will now loop at least once,
+	 assuring that we will not try to UNREAD two characters in a
+	 row.  */
+      FALLTHROUGH;
     default:
     default_label:
       if (c <= 040) goto retry;
diff --git a/src/regex.c b/src/regex.c
index 8e38a920cdb..ed848902086 100644
--- a/src/regex.c
+++ b/src/regex.c
@@ -2636,6 +2636,7 @@ regex_compile (const_re_char *pattern, size_t size,
 	  if ((syntax & RE_BK_PLUS_QM)
 	      || (syntax & RE_LIMITED_OPS))
 	    goto normal_char;
+	  FALLTHROUGH;
 	handle_plus:
 	case '*':
 	  /* If there is no previous pattern...  */
@@ -3086,6 +3087,7 @@ regex_compile (const_re_char *pattern, size_t size,
 				   with non-0. */
 				if (regnum == 0)
 				  FREE_STACK_RETURN (REG_BADPAT);
+				FALLTHROUGH;
 			      case '1': case '2': case '3': case '4':
 			      case '5': case '6': case '7': case '8': case '9':
 				regnum = 10*regnum + (c - '0'); break;
@@ -3905,8 +3907,7 @@ analyze_first (const_re_char *p, const_re_char *pend, char *fastmap,
 		 j < (1 << BYTEWIDTH); j++)
 	      fastmap[j] = 1;
 	  }
-
-	  /* Fallthrough */
+	  FALLTHROUGH;
 	case charset:
 	  if (!fastmap) break;
 	  not = (re_opcode_t) *(p - 1) == charset_not;
@@ -6182,8 +6183,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, const_re_char *string1,
 	    case on_failure_jump_nastyloop:
 	      assert ((re_opcode_t)pat[-2] == no_op);
 	      PUSH_FAILURE_POINT (pat - 2, str);
-	      /* Fallthrough */
-
+	      FALLTHROUGH;
 	    case on_failure_jump_loop:
 	    case on_failure_jump:
 	    case succeed_n:
diff --git a/src/search.c b/src/search.c
index 1223cbf07cc..19e789dfa87 100644
--- a/src/search.c
+++ b/src/search.c
@@ -1804,6 +1804,7 @@ boyer_moore (EMACS_INT n, unsigned char *base_pat,
     {
       /* Setup translate_prev_byte1/2/3/4 from CHAR_BASE.  Only a
 	 byte following them are the target of translation.  */
+      eassume (0x80 <= char_base && char_base <= MAX_CHAR);
       unsigned char str[MAX_MULTIBYTE_LENGTH];
       int cblen = CHAR_STRING (char_base, str);
 
diff --git a/src/syntax.c b/src/syntax.c
index 7aa43e6e5c7..dcaca22f0e2 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -810,6 +810,7 @@ back_comment (ptrdiff_t from, ptrdiff_t from_byte, ptrdiff_t stop,
 	case Sstring_fence:
 	case Scomment_fence:
 	  c = (code == Sstring_fence ? ST_STRING_STYLE : ST_COMMENT_STYLE);
+	  FALLTHROUGH;
 	case Sstring:
 	  /* Track parity of quotes.  */
 	  if (string_style == -1)
@@ -2690,6 +2691,7 @@ scan_lists (EMACS_INT from, EMACS_INT count, EMACS_INT depth, bool sexpflag)
 		goto lose;
 	      INC_BOTH (from, from_byte);
 	      /* Treat following character as a word constituent.  */
+	      FALLTHROUGH;
 	    case Sword:
 	    case Ssymbol:
 	      if (depth || !sexpflag) break;
@@ -2721,7 +2723,7 @@ scan_lists (EMACS_INT from, EMACS_INT count, EMACS_INT depth, bool sexpflag)
 
 	    case Scomment_fence:
 	      comstyle = ST_COMMENT_STYLE;
-	      /* FALLTHROUGH */
+	      FALLTHROUGH;
 	    case Scomment:
 	      if (!parse_sexp_ignore_comments) break;
 	      UPDATE_SYNTAX_TABLE_FORWARD (from);
@@ -2753,7 +2755,7 @@ scan_lists (EMACS_INT from, EMACS_INT count, EMACS_INT depth, bool sexpflag)
 		  goto close1;
 		}
 	      mathexit = 1;
-
+	      FALLTHROUGH;
 	    case Sopen:
 	      if (!++depth) goto done;
 	      break;
@@ -2909,7 +2911,7 @@ scan_lists (EMACS_INT from, EMACS_INT count, EMACS_INT depth, bool sexpflag)
 		  goto open2;
 		}
 	      mathexit = 1;
-
+	      FALLTHROUGH;
 	    case Sclose:
 	      if (!++depth) goto done2;
 	      break;
diff --git a/src/xterm.c b/src/xterm.c
index e9068830f85..c8836b7ca78 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -2005,9 +2005,9 @@ x_draw_glyphless_glyph_string_foreground (struct glyph_string *s)
 	}
       else if (glyph->u.glyphless.method == GLYPHLESS_DISPLAY_HEX_CODE)
 	{
-	  sprintf (buf, "%0*X",
-		   glyph->u.glyphless.ch < 0x10000 ? 4 : 6,
-		   glyph->u.glyphless.ch + 0u);
+	  unsigned int ch = glyph->u.glyphless.ch;
+	  eassume (ch <= MAX_CHAR);
+	  sprintf (buf, "%0*X", ch < 0x10000 ? 4 : 6, ch);
 	  str = buf;
 	}
 
@@ -8949,7 +8949,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
         {
         case MappingModifier:
           x_find_modifier_meanings (dpyinfo);
-          /* This is meant to fall through.  */
+	  FALLTHROUGH;
         case MappingKeyboard:
           XRefreshKeyboardMapping ((XMappingEvent *) &event->xmapping);
         }