[src/trunk]: src/usr.bin/make make: clean up comments in Var_Parse

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/837535b1914a
branches:  trunk
changeset: 366092:837535b1914a
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sat May 14 12:25:16 2022 +0000

description:
make: clean up comments in Var_Parse

diffstat:

 usr.bin/make/var.c |  35 +++++++++++++++--------------------
 1 files changed, 15 insertions(+), 20 deletions(-)

diffs (78 lines):

diff -r f0b2c4b7ca5a -r 837535b1914a usr.bin/make/var.c
--- a/usr.bin/make/var.c        Sat May 14 11:43:25 2022 +0000
+++ b/usr.bin/make/var.c        Sat May 14 12:25:16 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: var.c,v 1.1020 2022/05/09 21:24:42 rillig Exp $        */
+/*     $NetBSD: var.c,v 1.1021 2022/05/14 12:25:16 rillig Exp $        */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -139,7 +139,7 @@
 #include "metachar.h"
 
 /*     "@(#)var.c      8.3 (Berkeley) 3/19/94" */
-MAKE_RCSID("$NetBSD: var.c,v 1.1020 2022/05/09 21:24:42 rillig Exp $");
+MAKE_RCSID("$NetBSD: var.c,v 1.1021 2022/05/14 12:25:16 rillig Exp $");
 
 /*
  * Variables are defined using one of the VAR=value assignments.  Their
@@ -4444,9 +4444,8 @@
  *
  * Input:
  *     *pp             The string to parse.
- *                     In CondParser_FuncCallEmpty, it may also point to the
- *                     "y" of "empty(VARNAME:Modifiers)", which is
- *                     syntactically the same.
+ *                     When called from CondParser_FuncCallEmpty, it can
+ *                     also point to the "y" of "empty(VARNAME:Modifiers)".
  *     scope           The scope for finding variables
  *     emode           Controls the exact details of parsing and evaluation
  *
@@ -4477,16 +4476,14 @@
 {
        const char *p = *pp;
        const char *const start = p;
-       /* true if have modifiers for the variable. */
-       bool haveModifier;
-       /* Starting character if variable in parens or braces. */
-       char startc;
-       /* Ending character if variable in parens or braces. */
-       char endc;
+       bool haveModifier;      /* true for ${VAR:...}, false for ${VAR} */
+       char startc;            /* the actual '{' or '(' or '\0' */
+       char endc;              /* the expected '}' or ')' or '\0' */
        /*
-        * true if the variable is local and we're expanding it in a
-        * non-local scope. This is done to support dynamic sources.
-        * The result is just the expression, unaltered.
+        * true if the expression is based on one of the 7 predefined
+        * variables that are local to a target, and the expression is
+        * expanded in a non-local scope.  The result is the text of the
+        * expression, unaltered.  This is needed to support dynamic sources.
         */
        bool dynamic;
        const char *extramodifiers;
@@ -4503,11 +4500,7 @@
        extramodifiers = NULL;  /* extra modifiers to apply first */
        dynamic = false;
 
-       /*
-        * Appease GCC, which thinks that the variable might not be
-        * initialized.
-        */
-       endc = '\0';
+       endc = '\0';            /* Appease GCC. */
 
        startc = p[1];
        if (startc != '(' && startc != '{') {
@@ -4540,7 +4533,9 @@
         * XXX: This assignment creates an alias to the current value of the
         * variable.  This means that as long as the value of the expression
         * stays the same, the value of the variable must not change.
-        * Using the '::=' modifier, it could be possible to do exactly this.
+        * Using the '::=' modifier, it could be possible to trigger exactly
+        * this situation.
+        *
         * At the bottom of this function, the resulting value is compared to
         * the then-current value of the variable.  This might also invoke
         * undefined behavior.