For now, we still make sure to allocate at least PATH_MAX characters
for the strbuf because resolve_symlink() doesn't know how to expand
the space for its return value.  (That will be fixed in a moment.)

Another alternative would be to just use a strbuf as scratch space in
lock_file() but then store a pointer to the naked string in struct
lock_file.  But lock_file objects are often reused.  By reusing the
same strbuf, we can avoid having to reallocate the string most times
when a lock_file object is reused.

Signed-off-by: Michael Haggerty <mhag...@alum.mit.edu>
---
 builtin/commit.c | 12 ++++++------
 builtin/reflog.c |  2 +-
 cache.h          |  2 +-
 config.c         |  6 +++---
 lockfile.c       | 45 +++++++++++++++++++--------------------------
 refs.c           |  6 +++---
 shallow.c        |  6 +++---
 7 files changed, 36 insertions(+), 43 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 2e2d8bb..1833595 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -330,7 +330,7 @@ static const char *prepare_index(int argc, const char 
**argv, const char *prefix
                        die(_("unable to create temporary index"));
 
                old_index_env = getenv(INDEX_ENVIRONMENT);
-               setenv(INDEX_ENVIRONMENT, index_lock.filename, 1);
+               setenv(INDEX_ENVIRONMENT, index_lock.filename.buf, 1);
 
                if (interactive_add(argc, argv, prefix, patch_interactive) != 0)
                        die(_("interactive add failed"));
@@ -341,10 +341,10 @@ static const char *prepare_index(int argc, const char 
**argv, const char *prefix
                        unsetenv(INDEX_ENVIRONMENT);
 
                discard_cache();
-               read_cache_from(index_lock.filename);
+               read_cache_from(index_lock.filename.buf);
 
                commit_style = COMMIT_NORMAL;
-               return index_lock.filename;
+               return index_lock.filename.buf;
        }
 
        /*
@@ -368,7 +368,7 @@ static const char *prepare_index(int argc, const char 
**argv, const char *prefix
                    close_lock_file(&index_lock))
                        die(_("unable to write new_index file"));
                commit_style = COMMIT_NORMAL;
-               return index_lock.filename;
+               return index_lock.filename.buf;
        }
 
        /*
@@ -453,9 +453,9 @@ static const char *prepare_index(int argc, const char 
**argv, const char *prefix
                die(_("unable to write temporary index file"));
 
        discard_cache();
-       read_cache_from(false_lock.filename);
+       read_cache_from(false_lock.filename.buf);
 
-       return false_lock.filename;
+       return false_lock.filename.buf;
 }
 
 static int run_status(FILE *fp, const char *index_file, const char *prefix, 
int nowarn,
diff --git a/builtin/reflog.c b/builtin/reflog.c
index c12a9784..d7df34e 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -431,7 +431,7 @@ static int expire_reflog(const char *ref, const unsigned 
char *sha1, int unused,
                         write_str_in_full(lock->lock_fd, "\n") != 1 ||
                         close_ref(lock) < 0)) {
                        status |= error("Couldn't write %s",
-                               lock->lk->filename);
+                                       lock->lk->filename.buf);
                        unlink(newlog_path);
                } else if (rename(newlog_path, log_file)) {
                        status |= error("cannot rename %s to %s",
diff --git a/cache.h b/cache.h
index 59ce5cd..6ab2483 100644
--- a/cache.h
+++ b/cache.h
@@ -538,7 +538,7 @@ struct lock_file {
        int fd;
        pid_t owner;
        unsigned char flags;
-       char filename[PATH_MAX];
+       struct strbuf filename;
 };
 #define LOCK_DIE_ON_ERROR 1
 #define LOCK_NODEREF 2
diff --git a/config.c b/config.c
index 6821cef..78c3dad 100644
--- a/config.c
+++ b/config.c
@@ -1706,7 +1706,7 @@ out_free:
        return ret;
 
 write_err_out:
-       ret = write_error(lock->filename);
+       ret = write_error(lock->filename.buf);
        goto out_free;
 
 }
@@ -1821,7 +1821,7 @@ int git_config_rename_section_in_file(const char 
*config_filename,
                                }
                                store.baselen = strlen(new_name);
                                if (!store_write_section(out_fd, new_name)) {
-                                       ret = write_error(lock->filename);
+                                       ret = write_error(lock->filename.buf);
                                        goto out;
                                }
                                /*
@@ -1847,7 +1847,7 @@ int git_config_rename_section_in_file(const char 
*config_filename,
                        continue;
                length = strlen(output);
                if (write_in_full(out_fd, output, length) != length) {
-                       ret = write_error(lock->filename);
+                       ret = write_error(lock->filename.buf);
                        goto out;
                }
        }
diff --git a/lockfile.c b/lockfile.c
index bf018b5..3befd7e 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -196,13 +196,6 @@ static char *resolve_symlink(char *p, size_t s)
 
 static int lock_file(struct lock_file *lk, const char *path, int flags)
 {
-       /*
-        * subtract LOCK_SUFFIX_LEN from size to make sure there's
-        * room for adding ".lock" for the lock file name:
-        */
-       static const size_t max_path_len = sizeof(lk->filename) -
-                                          LOCK_SUFFIX_LEN;
-
        if (!lock_file_list) {
                /* One-time initialization */
                sigchain_push_common(remove_lock_file_on_signal);
@@ -216,26 +209,26 @@ static int lock_file(struct lock_file *lk, const char 
*path, int flags)
                lk->fd = -1;
                lk->owner = 0;
                lk->flags |= LOCK_FLAGS_ON_LIST;
-               lk->filename[0] = 0;
+               strbuf_init(&lk->filename, PATH_MAX);
                lk->next = lock_file_list;
                lock_file_list = lk;
        }
 
-       if (strlen(path) >= max_path_len)
-               return -1;
-       strcpy(lk->filename, path);
-       if (!(flags & LOCK_NODEREF))
-               resolve_symlink(lk->filename, max_path_len);
-       strcat(lk->filename, ".lock");
-       lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
+       strbuf_addstr(&lk->filename, path);
+       if (!(flags & LOCK_NODEREF)) {
+               resolve_symlink(lk->filename.buf, lk->filename.alloc);
+               strbuf_setlen(&lk->filename, strlen(lk->filename.buf));
+       }
+       strbuf_addstr(&lk->filename, ".lock");
+       lk->fd = open(lk->filename.buf, O_RDWR | O_CREAT | O_EXCL, 0666);
        if (lk->fd < 0) {
-               lk->filename[0] = 0;
+               strbuf_reset(&lk->filename);
                return -1;
        }
        lk->owner = getpid();
        lk->flags |= LOCK_FLAGS_LOCKFILE_ACTIVE;
-       if (adjust_shared_perm(lk->filename)) {
-               error("cannot fix permission bits on %s", lk->filename);
+       if (adjust_shared_perm(lk->filename.buf)) {
+               error("cannot fix permission bits on %s", lk->filename.buf);
                rollback_lock_file(lk);
                return -1;
        }
@@ -326,14 +319,14 @@ int commit_lock_file(struct lock_file *lk)
                return 0;
 
        /* remove ".lock": */
-       strbuf_add(&result_file, lk->filename,
-                  strlen(lk->filename) - LOCK_SUFFIX_LEN);
-       err = rename(lk->filename, result_file.buf);
+       strbuf_add(&result_file, lk->filename.buf,
+                  lk->filename.len - LOCK_SUFFIX_LEN);
+       err = rename(lk->filename.buf, result_file.buf);
        strbuf_reset(&result_file);
        if (err)
                return -1;
        lk->flags &= ~LOCK_FLAGS_LOCKFILE_ACTIVE;
-       lk->filename[0] = 0;
+       strbuf_reset(&lk->filename);
        return 0;
 }
 
@@ -355,10 +348,10 @@ int commit_locked_index(struct lock_file *lk)
        if (alternate_index_output) {
                if (lk->fd >= 0 && close_lock_file(lk))
                        return -1;
-               if (rename(lk->filename, alternate_index_output))
+               if (rename(lk->filename.buf, alternate_index_output))
                        return -1;
                lk->flags &= ~LOCK_FLAGS_LOCKFILE_ACTIVE;
-               lk->filename[0] = 0;
+               strbuf_reset(&lk->filename);
                return 0;
        }
        else
@@ -370,8 +363,8 @@ void rollback_lock_file(struct lock_file *lk)
        if (lk->flags & LOCK_FLAGS_LOCKFILE_ACTIVE) {
                if (lk->fd >= 0)
                        close_lock_file(lk);
-               unlink_or_warn(lk->filename);
+               unlink_or_warn(lk->filename.buf);
                lk->flags &= ~LOCK_FLAGS_LOCKFILE_ACTIVE;
-               lk->filename[0] = 0;
+               strbuf_reset(&lk->filename);
        }
 }
diff --git a/refs.c b/refs.c
index cd471ab..15d9e04 100644
--- a/refs.c
+++ b/refs.c
@@ -2489,8 +2489,8 @@ static int delete_ref_loose(struct ref_lock *lock, int 
flag)
                 * loose.  The loose file name is the same as the
                 * lockfile name, minus ".lock":
                 */
-               char *loose_filename = xmemdupz(lock->lk->filename,
-                                               strlen(lock->lk->filename) - 5);
+               char *loose_filename = xmemdupz(lock->lk->filename.buf,
+                                               lock->lk->filename.len - 5);
                int err = unlink_or_warn(loose_filename);
                free(loose_filename);
                if (err && errno != ENOENT)
@@ -2828,7 +2828,7 @@ int write_ref_sha1(struct ref_lock *lock,
        if (write_in_full(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
            write_in_full(lock->lock_fd, &term, 1) != 1
                || close_ref(lock) < 0) {
-               error("Couldn't write %s", lock->lk->filename);
+               error("Couldn't write %s", lock->lk->filename.buf);
                unlock_ref(lock);
                return -1;
        }
diff --git a/shallow.c b/shallow.c
index 0b267b6..cb29a66 100644
--- a/shallow.c
+++ b/shallow.c
@@ -269,8 +269,8 @@ void setup_alternate_shallow(struct lock_file *shallow_lock,
        if (write_shallow_commits(&sb, 0, extra)) {
                if (write_in_full(fd, sb.buf, sb.len) != sb.len)
                        die_errno("failed to write to %s",
-                                 shallow_lock->filename);
-               *alternate_shallow_file = shallow_lock->filename;
+                                 shallow_lock->filename.buf);
+               *alternate_shallow_file = shallow_lock->filename.buf;
        } else
                /*
                 * is_repository_shallow() sees empty string as "no
@@ -316,7 +316,7 @@ void prune_shallow(int show_only)
        if (write_shallow_commits_1(&sb, 0, NULL, SEEN_ONLY)) {
                if (write_in_full(fd, sb.buf, sb.len) != sb.len)
                        die_errno("failed to write to %s",
-                                 shallow_lock.filename);
+                                 shallow_lock.filename.buf);
                commit_lock_file(&shallow_lock);
        } else {
                unlink(git_path("shallow"));
-- 
1.9.1

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