[src/trunk]: src/usr.bin/make make(1): reduce number of stat fields returned ...

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

details:   https://anonhg.NetBSD.org/src/rev/6c21ed1fe45b
branches:  trunk
changeset: 938097:6c21ed1fe45b
user:      rillig <rillig%NetBSD.org@localhost>
date:      Wed Sep 02 04:08:54 2020 +0000

description:
make(1): reduce number of stat fields returned by cached_stat

Only st_mtime and st_mode are actually filled, the remaining fields had
been set to zero.  To prevent these from ever being accessed, a custom
struct make_stat replaces the previously used struct stat.

The fields in struct make_stat are intentionally named different from
the fields in struct stat because NetBSD and some other operating
systems define st_mtime as a macro, and that would not work in a field
declaration.

diffstat:

 usr.bin/make/dir.c  |  63 ++++++++++++++++++++++++++--------------------------
 usr.bin/make/dir.h  |  10 +++++++-
 usr.bin/make/make.h |   4 +--
 usr.bin/make/meta.c |  21 +++++++++--------
 4 files changed, 53 insertions(+), 45 deletions(-)

diffs (truncated from 328 to 300 lines):

diff -r d072187a81e7 -r 6c21ed1fe45b usr.bin/make/dir.c
--- a/usr.bin/make/dir.c        Wed Sep 02 04:06:43 2020 +0000
+++ b/usr.bin/make/dir.c        Wed Sep 02 04:08:54 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dir.c,v 1.132 2020/09/02 03:28:12 rillig Exp $ */
+/*     $NetBSD: dir.c,v 1.133 2020/09/02 04:08:54 rillig Exp $ */
 
 /*
  * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
@@ -70,14 +70,14 @@
  */
 
 #ifndef MAKE_NATIVE
-static char rcsid[] = "$NetBSD: dir.c,v 1.132 2020/09/02 03:28:12 rillig Exp $";
+static char rcsid[] = "$NetBSD: dir.c,v 1.133 2020/09/02 04:08:54 rillig Exp $";
 #else
 #include <sys/cdefs.h>
 #ifndef lint
 #if 0
 static char sccsid[] = "@(#)dir.c      8.2 (Berkeley) 1/2/94";
 #else
-__RCSID("$NetBSD: dir.c,v 1.132 2020/09/02 03:28:12 rillig Exp $");
+__RCSID("$NetBSD: dir.c,v 1.133 2020/09/02 04:08:54 rillig Exp $");
 #endif
 #endif /* not lint */
 #endif
@@ -282,13 +282,13 @@
     CST_UPDATE = 0x02          /* ignore existing cached entry */
 } CachedStatsFlags;
 
-/* Returns 0 and the result of stat(2) or lstat(2) in *st, or -1 on error.
- * Only st->st_mode and st->st_mtime are filled. */
+/* Returns 0 and the result of stat(2) or lstat(2) in *mst, or -1 on error. */
 static int
-cached_stats(Hash_Table *htp, const char *pathname, struct stat *st,
+cached_stats(Hash_Table *htp, const char *pathname, struct make_stat *mst,
             CachedStatsFlags flags)
 {
     Hash_Entry *entry;
+    struct stat sys_st;
     struct cache_st *cst;
     int rc;
 
@@ -300,22 +300,23 @@
     if (entry && !(flags & CST_UPDATE)) {
        cst = Hash_GetValue(entry);
 
-       memset(st, 0, sizeof(*st));
-       st->st_mode = cst->mode;
-       st->st_mtime = (flags & CST_LSTAT) ? cst->lmtime : cst->mtime;
-       if (st->st_mtime) {
+       mst->mst_mode = cst->mode;
+       mst->mst_mtime = (flags & CST_LSTAT) ? cst->lmtime : cst->mtime;
+       if (mst->mst_mtime) {
            DIR_DEBUG2("Using cached time %s for %s\n",
-                      Targ_FmtTime(st->st_mtime), pathname);
+                      Targ_FmtTime(mst->mst_mtime), pathname);
            return 0;
        }
     }
 
-    rc = (flags & CST_LSTAT) ? lstat(pathname, st) : stat(pathname, st);
+    rc = (flags & CST_LSTAT)
+        ? lstat(pathname, &sys_st)
+        : stat(pathname, &sys_st);
     if (rc == -1)
        return -1;
 
-    if (st->st_mtime == 0)
-       st->st_mtime = 1;       /* avoid confusion with missing file */
+    if (sys_st.st_mtime == 0)
+       sys_st.st_mtime = 1;    /* avoid confusion with missing file */
 
     if (entry == NULL)
        entry = Hash_CreateEntry(htp, pathname, NULL);
@@ -325,25 +326,25 @@
     }
     cst = Hash_GetValue(entry);
     if (flags & CST_LSTAT) {
-       cst->lmtime = st->st_mtime;
+       cst->lmtime = sys_st.st_mtime;
     } else {
-       cst->mtime = st->st_mtime;
+       cst->mtime = sys_st.st_mtime;
     }
-    cst->mode = st->st_mode;
+    cst->mode = sys_st.st_mode;
     DIR_DEBUG2("   Caching %s for %s\n",
-              Targ_FmtTime(st->st_mtime), pathname);
+              Targ_FmtTime(sys_st.st_mtime), pathname);
 
     return 0;
 }
 
 int
-cached_stat(const char *pathname, struct stat *st)
+cached_stat(const char *pathname, struct make_stat *st)
 {
     return cached_stats(&mtimes, pathname, st, 0);
 }
 
 int
-cached_lstat(const char *pathname, struct stat *st)
+cached_lstat(const char *pathname, struct make_stat *st)
 {
     return cached_stats(&lmtimes, pathname, st, CST_LSTAT);
 }
@@ -935,7 +936,7 @@
 static char *
 DirLookupSubdir(Path *p, const char *name)
 {
-    struct stat stb;           /* Buffer for stat, if necessary */
+    struct make_stat mst;
     char *file;                        /* the current filename to check */
 
     if (p != dot) {
@@ -949,7 +950,7 @@
 
     DIR_DEBUG1("checking %s ...\n", file);
 
-    if (cached_stat(file, &stb) == 0) {
+    if (cached_stat(file, &mst) == 0) {
        nearmisses += 1;
        return file;
     }
@@ -1069,7 +1070,7 @@
     const char *cp;            /* Terminal name of file */
     Boolean hasLastDot = FALSE;        /* true we should search dot last */
     Boolean hasSlash;          /* true if 'name' contains a / */
-    struct stat stb;           /* Buffer for stat, if necessary */
+    struct make_stat mst;      /* Buffer for stat, if necessary */
     const char *trailing_dot = ".";
 
     /*
@@ -1312,7 +1313,7 @@
     DIR_DEBUG1("   Looking for \"%s\" ...\n", name);
 
     bigmisses += 1;
-    if (cached_stat(name, &stb) == 0) {
+    if (cached_stat(name, &mst) == 0) {
        return bmake_strdup(name);
     }
 
@@ -1346,7 +1347,7 @@
 Dir_FindHereOrAbove(const char *here, const char *search_path,
                    char *result, int result_len)
 {
-    struct stat st;
+    struct make_stat mst;
     char dirbase[MAXPATHLEN + 1], *dirbase_end;
     char try[MAXPATHLEN + 1], *try_end;
 
@@ -1359,12 +1360,12 @@
 
        /* try and stat(2) it ... */
        snprintf(try, sizeof(try), "%s/%s", dirbase, search_path);
-       if (cached_stat(try, &st) != -1) {
+       if (cached_stat(try, &mst) != -1) {
            /*
             * success!  if we found a file, chop off
             * the filename so we return a directory.
             */
-           if ((st.st_mode & S_IFMT) != S_IFDIR) {
+           if ((mst.mst_mode & S_IFMT) != S_IFDIR) {
                try_end = try + strlen(try);
                while (try_end > try && *try_end != '/')
                    try_end--;
@@ -1417,7 +1418,7 @@
 Dir_MTime(GNode *gn, Boolean recheck)
 {
     char *fullName;            /* the full pathname of name */
-    struct stat stb;           /* buffer for finding the mod time */
+    struct make_stat mst;      /* buffer for finding the mod time */
 
     if (gn->type & OP_ARCHV) {
        return Arch_MTime(gn);
@@ -1468,13 +1469,13 @@
        fullName = bmake_strdup(gn->name);
     }
 
-    if (cached_stats(&mtimes, fullName, &stb, recheck ? CST_UPDATE : 0) < 0) {
+    if (cached_stats(&mtimes, fullName, &mst, recheck ? CST_UPDATE : 0) < 0) {
        if (gn->type & OP_MEMBER) {
            if (fullName != gn->path)
                free(fullName);
            return Arch_MemMTime(gn);
        } else {
-           stb.st_mtime = 0;
+           mst.mst_mtime = 0;
        }
     }
 
@@ -1482,7 +1483,7 @@
        gn->path = fullName;
     }
 
-    gn->mtime = stb.st_mtime;
+    gn->mtime = mst.mst_mtime;
     return gn->mtime;
 }
 
diff -r d072187a81e7 -r 6c21ed1fe45b usr.bin/make/dir.h
--- a/usr.bin/make/dir.h        Wed Sep 02 04:06:43 2020 +0000
+++ b/usr.bin/make/dir.h        Wed Sep 02 04:08:54 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dir.h,v 1.22 2020/09/01 20:17:18 rillig Exp $  */
+/*     $NetBSD: dir.h,v 1.23 2020/09/02 04:08:54 rillig Exp $  */
 
 /*
  * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
@@ -85,6 +85,11 @@
     Hash_Table    files;       /* Hash set of files in directory */
 } Path;
 
+struct make_stat {
+    time_t mst_mtime;
+    mode_t mst_mode;
+};
+
 void Dir_Init(void);
 void Dir_InitDir(const char *);
 void Dir_InitCur(const char *);
@@ -105,4 +110,7 @@
 void Dir_Destroy(void *);
 void *Dir_CopyDir(void *);
 
+int cached_lstat(const char *, struct make_stat *);
+int cached_stat(const char *, struct make_stat *);
+
 #endif /* MAKE_DIR_H */
diff -r d072187a81e7 -r 6c21ed1fe45b usr.bin/make/make.h
--- a/usr.bin/make/make.h       Wed Sep 02 04:06:43 2020 +0000
+++ b/usr.bin/make/make.h       Wed Sep 02 04:08:54 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: make.h,v 1.135 2020/09/02 03:28:12 rillig Exp $        */
+/*     $NetBSD: make.h,v 1.136 2020/09/02 04:08:54 rillig Exp $        */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -537,8 +537,6 @@
 Boolean Main_SetObjdir(const char *, ...) MAKE_ATTR_PRINTFLIKE(1, 2);
 int mkTempFile(const char *, char **);
 int str2Lst_Append(Lst, char *, const char *);
-int cached_lstat(const char *, struct stat *);
-int cached_stat(const char *, struct stat *);
 void GNode_FprintDetails(FILE *, const char *, const GNode *, const char *);
 
 #ifdef __GNUC__
diff -r d072187a81e7 -r 6c21ed1fe45b usr.bin/make/meta.c
--- a/usr.bin/make/meta.c       Wed Sep 02 04:06:43 2020 +0000
+++ b/usr.bin/make/meta.c       Wed Sep 02 04:08:54 2020 +0000
@@ -1,4 +1,4 @@
-/*      $NetBSD: meta.c,v 1.112 2020/08/30 11:15:05 rillig Exp $ */
+/*      $NetBSD: meta.c,v 1.113 2020/09/02 04:08:54 rillig Exp $ */
 
 /*
  * Implement 'meta' mode.
@@ -43,6 +43,7 @@
 #endif
 
 #include "make.h"
+#include "dir.h"
 #include "job.h"
 
 #ifdef USE_FILEMON
@@ -399,7 +400,7 @@
 meta_needed(GNode *gn, const char *dname, const char *tname,
             char *objdir, int verbose)
 {
-    struct stat fs;
+    struct make_stat mst;
 
     if (verbose)
        verbose = DEBUG(META);
@@ -433,7 +434,7 @@
     }
 
     /* The object directory may not exist. Check it.. */
-    if (cached_stat(dname, &fs) != 0) {
+    if (cached_stat(dname, &mst) != 0) {
        if (verbose)
            fprintf(debug_file, "Skipping meta for %s: no .OBJDIR\n",
                    gn->name);
@@ -1124,7 +1125,7 @@
        int pid;
        int x;
        LstNode ln;
-       struct stat fs;
+       struct make_stat mst;
 
        if (!buf) {
            bufsz = 8 * BUFSIZ;
@@ -1389,8 +1390,8 @@
                    if ((strstr("tmp", p)))
                        break;
 
-                   if ((link_src != NULL && cached_lstat(p, &fs) < 0) ||
-                       (link_src == NULL && cached_stat(p, &fs) < 0)) {
+                   if ((link_src != NULL && cached_lstat(p, &mst) < 0) ||
+                       (link_src == NULL && cached_stat(p, &mst) < 0)) {