From 8674b0c3d161bd367ff63c6a8fb290fec0122d05 Mon Sep 17 00:00:00 2001
From: Phlosioneer <mattmdrr2@gmail.com>
Date: Mon, 20 Nov 2017 18:04:49 -0500
Subject: [PATCH] syntax.c: Fix maybe-uninitialized warning (#7596)

When building in release mode, gcc generated a maybe-initialized
warning in get_syn_options. The warning is both right and wrong;
there is an execution path where the len variable is not
initialized in the code:
...
int len;
...
for (fidx = ARRAY_SIZE(flagtab); --fidx >= 0; ) {
  p = flagtab[fidx].name;
  int i;
  for (i = 0, len = 0; p[i] != NUL; i += 2, ++len)
    if (arg[len] != p[i] && arg[len] != p[i + 1])
      break;
  // <snip>
}
...
  arg = skipwhite(arg + len);
...

The initial for loop will not execute if ARRAY_SIZE(flagtab) == 0,
and thus len will never be initialized. flagtab is a local-static
variable, initialized to a long array of structured data, so
ARRAY_SIZE(flagtab) can't be 0.

However, gcc doesn't recognize ARRAY_SIZE(flagtab) as a constant.
There are any number of reasons this could happen. In any case,
the message can be fixed with a len=0 before the first for loop.

In addition to the above warning, I've labeled flagtab and
first_letters as const. They should never change.
---
 src/nvim/syntax.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index 65490768c4..d28e996581 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -4009,10 +4009,10 @@ get_syn_options (
 {
   char_u      *gname_start, *gname;
   int syn_id;
-  int len;
+  int len = 0;
   char        *p;
   int fidx;
-  static struct flag {
+  static const struct flag {
     char    *name;
     int argtype;
     int flags;
@@ -4035,7 +4035,7 @@ get_syn_options (
                   {"cCoOnNtTaAiInNsS",        1,      0},
                   {"cCoOnNtTaAiInNeEdDiInN",  2,      0},
                   {"nNeExXtTgGrRoOuUpP",      3,      0},};
-  static char *first_letters = "cCoOkKeEtTsSgGdDfFnN";
+  static const char *const first_letters = "cCoOkKeEtTsSgGdDfFnN";
 
   if (arg == NULL)              /* already detected error */
     return NULL;
@@ -4055,9 +4055,10 @@ get_syn_options (
     for (fidx = ARRAY_SIZE(flagtab); --fidx >= 0; ) {
       p = flagtab[fidx].name;
       int i;
-      for (i = 0, len = 0; p[i] != NUL; i += 2, ++len)
+      for (i = 0, len = 0; p[i] != NUL; i += 2, ++len) {
         if (arg[len] != p[i] && arg[len] != p[i + 1])
           break;
+      }
       if (p[i] == NUL && (ascii_iswhite(arg[len])
                           || (flagtab[fidx].argtype > 0
                               ? arg[len] == '='