[src/trunk]: src/usr.bin/make make(1): document that indirect modifiers fall ...

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

details:   https://anonhg.NetBSD.org/src/rev/ce637d9f8571
branches:  trunk
changeset: 1017290:ce637d9f8571
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sun Dec 20 19:02:28 2020 +0000

description:
make(1): document that indirect modifiers fall back to SysV modifiers

diffstat:

 usr.bin/make/var.c |  38 ++++++++++++++++++++++++--------------
 1 files changed, 24 insertions(+), 14 deletions(-)

diffs (93 lines):

diff -r 69ca3a7516bc -r ce637d9f8571 usr.bin/make/var.c
--- a/usr.bin/make/var.c        Sun Dec 20 18:23:24 2020 +0000
+++ b/usr.bin/make/var.c        Sun Dec 20 19:02:28 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: var.c,v 1.751 2020/12/20 18:23:24 rillig Exp $ */
+/*     $NetBSD: var.c,v 1.752 2020/12/20 19:02:28 rillig Exp $ */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -131,7 +131,7 @@
 #include "metachar.h"
 
 /*     "@(#)var.c      8.3 (Berkeley) 3/19/94" */
-MAKE_RCSID("$NetBSD: var.c,v 1.751 2020/12/20 18:23:24 rillig Exp $");
+MAKE_RCSID("$NetBSD: var.c,v 1.752 2020/12/20 19:02:28 rillig Exp $");
 
 typedef enum VarFlags {
        VAR_NONE        = 0,
@@ -3420,13 +3420,30 @@
                            VarExprFlags *, GNode *, VarEvalFlags, void **);
 
 typedef enum ApplyModifiersIndirectResult {
+       /* The indirect modifiers have been applied successfully. */
        AMIR_CONTINUE,
+       /* Fall back to the SysV modifier. */
        AMIR_APPLY_MODS,
+       /* Error out. */
        AMIR_OUT
 } ApplyModifiersIndirectResult;
 
-/* While expanding a variable expression, expand and apply indirect
- * modifiers such as in ${VAR:${M_indirect}}. */
+/*
+ * While expanding a variable expression, expand and apply indirect modifiers,
+ * such as in ${VAR:${M_indirect}}.
+ *
+ * All indirect modifiers of a group must come from a single variable
+ * expression.  ${VAR:${M1}} is valid but ${VAR:${M1}${M2}} is not.
+ *
+ * Multiple groups of indirect modifiers can be chained by separating them
+ * with colons.  ${VAR:${M1}:${M2}} contains 2 indirect modifiers.
+ *
+ * If the variable expression is not followed by st->endc or ':', fall
+ * back to trying the SysV modifier, such as in ${VAR:${FROM}=${TO}}.
+ *
+ * The expression ${VAR:${M1}${M2}} is not treated as an indirect
+ * modifier, and it is neither a SysV modifier but a parse error.
+ */
 static ApplyModifiersIndirectResult
 ApplyModifiersIndirect(ApplyModifiersState *st, const char **pp,
                       char **inout_val, void **inout_freeIt)
@@ -3437,11 +3454,6 @@
        (void)Var_Parse(&p, st->ctxt, st->eflags, &mods);
        /* TODO: handle errors */
 
-       /*
-        * If we have not parsed up to st->endc or ':', we are not
-        * interested.  This means the expression ${VAR:${M1}${M2}}
-        * is not accepted, but ${VAR:${M1}:${M2}} is.
-        */
        if (mods.str[0] != '\0' && *p != '\0' && *p != ':' && *p != st->endc) {
                if (opts.lint)
                        Parse_Error(PARSE_FATAL,
@@ -3450,9 +3462,6 @@
                            (int)(p - *pp), *pp);
 
                FStr_Done(&mods);
-               /* XXX: apply_mods doesn't sound like "not interested". */
-               /* XXX: Why is the indirect modifier parsed once more by
-                * apply_mods?  Try *pp = p here. */
                return AMIR_APPLY_MODS;
        }
 
@@ -3606,8 +3615,9 @@
                        if (amir == AMIR_CONTINUE)
                                continue;
                        if (amir == AMIR_OUT)
-                               goto out;
+                               break;
                }
+
                st.newVal = var_Error;  /* default value, in case of errors */
                mod = p;
 
@@ -3618,7 +3628,7 @@
                if (res == AMR_BAD)
                        goto bad_modifier;
        }
-out:
+
        *pp = p;
        assert(val != NULL);    /* Use var_Error or varUndefined instead. */
        *exprFlags = st.exprFlags;