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);
         }