[src/trunk]: src/usr.bin/mkdep mkdep: avoid memory allocation in findcc

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

details:   https://anonhg.NetBSD.org/src/rev/5db05524eb9c
branches:  trunk
changeset: 1023034:5db05524eb9c
user:      rillig <rillig%NetBSD.org@localhost>
date:      Fri Aug 20 06:36:10 2021 +0000

description:
mkdep: avoid memory allocation in findcc

This change takes the idea of handling strings as pairs in the form
(start, len) by Robert Elz from
https://mail-index.netbsd.org/source-changes-d/2021/08/20/msg013427.html
and expands it by avoiding one more memory allocation, for iterating the
PATH environment variable.

No functional change.

diffstat:

 tests/usr.bin/mkdep/Makefile    |   3 +-
 tests/usr.bin/mkdep/t_findcc.sh |  29 ++++++++++++++++++-
 usr.bin/mkdep/findcc.c          |  63 ++++++++++++++++++----------------------
 3 files changed, 58 insertions(+), 37 deletions(-)

diffs (158 lines):

diff -r 57b1c22b5236 -r 5db05524eb9c tests/usr.bin/mkdep/Makefile
--- a/tests/usr.bin/mkdep/Makefile      Fri Aug 20 05:45:19 2021 +0000
+++ b/tests/usr.bin/mkdep/Makefile      Fri Aug 20 06:36:10 2021 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.2 2021/08/11 20:42:26 rillig Exp $
+# $NetBSD: Makefile,v 1.3 2021/08/20 06:36:10 rillig Exp $
 
 .include <bsd.own.mk>
 
@@ -13,5 +13,6 @@
 SRCS=          h_findcc.c findcc.c
 CPPFLAGS+=     -I${NETBSDSRCDIR}/usr.bin/mkdep
 MAN.h_findcc=  # none
+WARNS=         6
 
 .include <bsd.test.mk>
diff -r 57b1c22b5236 -r 5db05524eb9c tests/usr.bin/mkdep/t_findcc.sh
--- a/tests/usr.bin/mkdep/t_findcc.sh   Fri Aug 20 05:45:19 2021 +0000
+++ b/tests/usr.bin/mkdep/t_findcc.sh   Fri Aug 20 06:36:10 2021 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: t_findcc.sh,v 1.2 2021/08/20 05:45:19 rillig Exp $
+# $NetBSD: t_findcc.sh,v 1.3 2021/08/20 06:36:10 rillig Exp $
 #
 # Copyright (c) 2021 The NetBSD Foundation, Inc.
 # All rights reserved.
@@ -51,6 +51,31 @@
                "$(atf_get_srcdir)"/h_findcc 'echo'
 }
 
+# A plain program name is searched in the PATH and, in this example, it is
+# found in '/bin', which comes second in the PATH.
+#
+atf_test_case base_found_second
+base_found_second_body() {
+       atf_check -o "inline:/bin/echo$n" \
+           env -i PATH='/nonexistent:/bin' \
+               "$(atf_get_srcdir)"/h_findcc 'echo'
+}
+
+# A plain program name is searched in the PATH and, in this example, it is
+# found in './bin', a relative path in the PATH, which is rather unusual in
+# practice.
+#
+atf_test_case base_found_reldir
+base_found_reldir_body() {
+       mkdir bin
+       echo '#! /bin/sh' > 'bin/reldir-echo'
+       chmod +x 'bin/reldir-echo'
+
+       atf_check -o "inline:bin/reldir-echo$n" \
+           env -i PATH='/nonexistent:bin' \
+               "$(atf_get_srcdir)"/h_findcc 'reldir-echo'
+}
+
 # The C compiler can be specified as a program with one or more arguments.
 # If the program name is a plain name without any slash, the argument is
 # discarded.
@@ -143,6 +168,8 @@
 atf_init_test_cases() {
        atf_add_test_case base_not_found
        atf_add_test_case base_found
+       atf_add_test_case base_found_second
+       atf_add_test_case base_found_reldir
        atf_add_test_case base_arg_found
 
        atf_add_test_case rel_not_found
diff -r 57b1c22b5236 -r 5db05524eb9c usr.bin/mkdep/findcc.c
--- a/usr.bin/mkdep/findcc.c    Fri Aug 20 05:45:19 2021 +0000
+++ b/usr.bin/mkdep/findcc.c    Fri Aug 20 06:36:10 2021 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: findcc.c,v 1.9 2021/08/20 05:45:19 rillig Exp $ */
+/* $NetBSD: findcc.c,v 1.10 2021/08/20 06:36:10 rillig Exp $ */
 
 /*-
  * Copyright (c) 1999 The NetBSD Foundation, Inc.
@@ -37,7 +37,7 @@
 #if !defined(lint)
 __COPYRIGHT("@(#) Copyright (c) 1999 The NetBSD Foundation, Inc.\
  All rights reserved.");
-__RCSID("$NetBSD: findcc.c,v 1.9 2021/08/20 05:45:19 rillig Exp $");
+__RCSID("$NetBSD: findcc.c,v 1.10 2021/08/20 06:36:10 rillig Exp $");
 #endif /* not lint */
 
 #include <sys/param.h>
@@ -49,47 +49,40 @@
 #include "findcc.h"
 
 char *
-findcc(const char *cc_command)
+findcc(const char *progname)
 {
-       char   *progname, *path, *dir, *next;
-       char   buffer[MAXPATHLEN];
-
-       if ((progname = strdup(cc_command)) == NULL)
-               return NULL;
+       char *cc;
+       const char *path, *dir;
+       char buffer[MAXPATHLEN];
+       size_t progname_len, dir_len;
 
-       if ((next = strchr(progname, ' ')) != NULL)
-               *next = '\0';
+       progname_len = strcspn(progname, " ");
 
-       if (strchr(progname, '/') != NULL) {
-               if (access(progname, X_OK) == 0)
-                       return progname;
-               free(progname);
+       if (memchr(progname, '/', progname_len) != NULL) {
+               if ((cc = strndup(progname, progname_len)) == NULL)
+                       return NULL;
+               if (access(cc, X_OK) == 0)
+                       return cc;
+               free(cc);
                return NULL;
        }
 
-       if (((path = getenv("PATH")) == NULL) ||
-           ((path = strdup(path)) == NULL)) {
-               free(progname);
+       if ((path = getenv("PATH")) == NULL)
                return NULL;
+
+       for (dir = path; *dir != '\0'; ) {
+               dir_len = strcspn(dir, ":");
+
+               if ((size_t)snprintf(buffer, sizeof(buffer), "%.*s/%.*s",
+                       (int)dir_len, dir, (int)progname_len, progname)
+                   < sizeof(buffer)
+                   && access(buffer, X_OK) == 0)
+                       return strdup(buffer);
+
+               dir += dir_len;
+               if (*dir == ':')
+                       dir++;
        }
 
-       dir = path;
-       while (dir != NULL) {
-               if ((next = strchr(dir, ':')) != NULL)
-                       *next++ = '\0';
-
-               if (snprintf(buffer, sizeof(buffer),
-                   "%s/%s", dir, progname) < (int)sizeof(buffer)) {
-                       if (access(buffer, X_OK) == 0) {
-                               free(path);
-                               free(progname);
-                               return strdup(buffer);
-                       }
-               }
-               dir = next;
-       }
-
-       free(path);
-       free(progname);
        return NULL;
 }