[src/trunk]: src/usr.bin/make make: reduce debug logging and memory allocatio...

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

details:   https://anonhg.NetBSD.org/src/rev/f3825874bd43
branches:  trunk
changeset: 954484:f3825874bd43
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sat Apr 10 22:09:53 2021 +0000

description:
make: reduce debug logging and memory allocation for ${:U...}

Expressions of the form ${:U...} are often generated by .for loops.
Since these expressions are not generated knowingly by the make user, do
not fill the debug log with them since that would interrupt the normal
reading flow of the -dv log for nested expressions.

diffstat:

 usr.bin/make/var.c |  40 ++++++++++++++++++++++++++++++++++++++--
 1 files changed, 38 insertions(+), 2 deletions(-)

diffs (75 lines):

diff -r 8b4d8cec3e6d -r f3825874bd43 usr.bin/make/var.c
--- a/usr.bin/make/var.c        Sat Apr 10 22:09:16 2021 +0000
+++ b/usr.bin/make/var.c        Sat Apr 10 22:09:53 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: var.c,v 1.912 2021/04/06 01:38:39 rillig Exp $ */
+/*     $NetBSD: var.c,v 1.913 2021/04/10 22:09:53 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 1.912 2021/04/06 01:38:39 rillig Exp $");
+MAKE_RCSID("$NetBSD: var.c,v 1.913 2021/04/10 22:09:53 rillig Exp $");
 
 /*
  * Variables are defined using one of the VAR=value assignments.  Their
@@ -437,6 +437,11 @@
        if (var == NULL) {
                char *env;
 
+               /*
+                * TODO: try setting an environment variable with the empty
+                *  name, which should be technically possible, just to see
+                *  how make reacts.  All .for loops should be broken then.
+                */
                if ((env = getenv(name)) != NULL) {
                        char *varname = bmake_strdup(name);
                        return VarNew(FStr_InitOwn(varname), env, true, false);
@@ -4381,6 +4386,34 @@
 #endif
 
 /*
+ * Expressions of the form ${:U...} with a trivial value are often generated
+ * by .for loops and are boring, therefore parse and evaluate them in a fast
+ * lane without debug logging.
+ */
+static bool
+Var_Parse_FastLane(const char **pp, VarEvalMode emode, FStr *out_value)
+{
+       const char *p;
+
+       p = *pp;
+       if (!(p[0] == '$' && p[1] == '{' && p[2] == ':' && p[3] == 'U'))
+               return false;
+
+       p += 4;
+       while (*p != '$' && *p != '{' && *p != ':' && *p != '\\' && *p != '}')
+               p++;
+       if (*p != '}')
+               return false;
+
+       if (emode == VARE_PARSE_ONLY)
+               *out_value = FStr_InitRefer("");
+       else
+               *out_value = FStr_InitOwn(bmake_strsedup(*pp + 4, p));
+       *pp = p + 1;
+       return true;
+}
+
+/*
  * Given the start of a variable expression (such as $v, $(VAR),
  * ${VAR:Mpattern}), extract the variable name and value, and the modifiers,
  * if any.  While doing that, apply the modifiers to the value of the
@@ -4439,6 +4472,9 @@
        Expr expr = Expr_Literal(NULL, FStr_InitRefer(NULL), emode,
            scope, DEF_REGULAR);
 
+       if (Var_Parse_FastLane(pp, emode, out_val))
+               return VPR_OK;
+
        DEBUG2(VAR, "Var_Parse: %s (%s)\n", start, VarEvalMode_Name[emode]);
 
        *out_val = FStr_InitRefer(NULL);