[src/trunk]: src/usr.bin/make make: explain non-obvious code around indirect ...

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

details:   https://anonhg.NetBSD.org/src/rev/c9672d99cd91
branches:  trunk
changeset: 953010:c9672d99cd91
user:      rillig <rillig%NetBSD.org@localhost>
date:      Tue Feb 23 15:03:56 2021 +0000

description:
make: explain non-obvious code around indirect variable modifiers

No functional change.

diffstat:

 usr.bin/make/var.c |  17 +++++++++++------
 1 files changed, 11 insertions(+), 6 deletions(-)

diffs (56 lines):

diff -r 6b474f6728cb -r c9672d99cd91 usr.bin/make/var.c
--- a/usr.bin/make/var.c        Tue Feb 23 15:00:01 2021 +0000
+++ b/usr.bin/make/var.c        Tue Feb 23 15:03:56 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: var.c,v 1.848 2021/02/23 14:27:27 rillig Exp $ */
+/*     $NetBSD: var.c,v 1.849 2021/02/23 15:03:56 rillig Exp $ */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -140,7 +140,7 @@
 #include "metachar.h"
 
 /*     "@(#)var.c      8.3 (Berkeley) 3/19/94" */
-MAKE_RCSID("$NetBSD: var.c,v 1.848 2021/02/23 14:27:27 rillig Exp $");
+MAKE_RCSID("$NetBSD: var.c,v 1.849 2021/02/23 15:03:56 rillig Exp $");
 
 typedef enum VarFlags {
        VFL_NONE        = 0,
@@ -3639,7 +3639,7 @@
        /* The indirect modifiers have been applied successfully. */
        AMIR_CONTINUE,
        /* Fall back to the SysV modifier. */
-       AMIR_APPLY_MODS,
+       AMIR_SYSV,
        /* Error out. */
        AMIR_OUT
 } ApplyModifiersIndirectResult;
@@ -3669,7 +3669,7 @@
 
        if (mods.str[0] != '\0' && *p != '\0' && *p != ':' && *p != st->endc) {
                FStr_Done(&mods);
-               return AMIR_APPLY_MODS;
+               return AMIR_SYSV;
        }
 
        DEBUG3(VAR, "Indirect modifier \"%s\" from \"%.*s\"\n",
@@ -3796,12 +3796,17 @@
                ApplyModifierResult res;
 
                if (*p == '$') {
-                       ApplyModifiersIndirectResult amir;
-                       amir = ApplyModifiersIndirect(&st, &p);
+                       ApplyModifiersIndirectResult amir =
+                           ApplyModifiersIndirect(&st, &p);
                        if (amir == AMIR_CONTINUE)
                                continue;
                        if (amir == AMIR_OUT)
                                break;
+                       /*
+                        * It's neither '${VAR}:' nor '${VAR}}'.  Try to parse
+                        * it as a SysV modifier, as that is the only modifier
+                        * that can start with '$'.
+                        */
                }
 
                mod = p;