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apply: refactor `struct image` to use a `struct strbuf` 

The `struct image` uses a character array to track the pre- or postimage
of a patch operation. This has multiple downsides:

  - It is somewhat hard to track memory ownership. In fact, we have
    several memory leaks in git-apply(1) because we do not (and cannot
    easily) free the buffer in all situations.

  - We have to reinvent the wheel and manually implement a lot of
    functionality that would already be provided by `struct strbuf`.

  - We have to carefully track whether `update_pre_post_images()` can do
    an in-place update of the postimage or whether it has to allocate a
    new buffer for it.

This is all rather cumbersome, and especially `update_pre_post_images()`
is really hard to understand as a consequence even though what it is
doing is rather trivial.

Refactor the code to use a `struct strbuf` instead, addressing all of
the above. Like this we can easily perform in-place updates in all
situations, the logic to perform those updates becomes way simpler and
the lifetime of the buffer becomes a ton easier to track.

This refactoring also plugs some leaking buffers as a side effect.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Patrick Steinhardt 2024-09-17 12:08:08 +02:00 committed by Junio C Hamano
parent e73686f6e4
commit 3fc4eab466
6 changed files with 79 additions and 123 deletions
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194
apply.c
View File

@ -277,12 +277,13 @@ struct line {
* This represents a "file", which is an array of "lines".
*/
struct image {
char *buf;
size_t len;
struct strbuf buf;
struct line *line;
size_t line_nr, line_alloc;
};
#define IMAGE_INIT { 0 }
#define IMAGE_INIT { \
.buf = STRBUF_INIT, \
}

static void image_init(struct image *image)
{
@ -292,7 +293,7 @@ static void image_init(struct image *image)

static void image_clear(struct image *image)
{
free(image->buf);
strbuf_release(&image->buf);
free(image->line);
image_init(image);
}
@ -329,14 +330,13 @@ static void image_prepare(struct image *image, char *buf, size_t len,
const char *cp, *ep;

image_clear(image);
image->buf = buf;
image->len = len;
strbuf_attach(&image->buf, buf, len, len + 1);

if (!prepare_linetable)
return;

ep = image->buf + image->len;
cp = image->buf;
ep = image->buf.buf + image->buf.len;
cp = image->buf.buf;
while (cp < ep) {
const char *next;
for (next = cp; next < ep && *next != '\n'; next++)
@ -350,8 +350,7 @@ static void image_prepare(struct image *image, char *buf, size_t len,

static void image_remove_first_line(struct image *img)
{
img->buf += img->line[0].len;
img->len -= img->line[0].len;
strbuf_remove(&img->buf, 0, img->line[0].len);
img->line_nr--;
if (img->line_nr)
MOVE_ARRAY(img->line, img->line + 1, img->line_nr);
@ -359,7 +358,9 @@ static void image_remove_first_line(struct image *img)

static void image_remove_last_line(struct image *img)
{
img->len -= img->line[--img->line_nr].len;
size_t last_line_len = img->line[img->line_nr - 1].len;
strbuf_setlen(&img->buf, img->buf.len - last_line_len);
img->line_nr--;
}

/* fmt must contain _one_ %s and no other substitution */
@ -2308,19 +2309,16 @@ static int read_old_data(struct stat *st, struct patch *patch,

/*
* Update the preimage, and the common lines in postimage,
* from buffer buf of length len. If postlen is 0 the postimage
* is updated in place, otherwise it's updated on a new buffer
* of length postlen
* from buffer buf of length len.
*/

static void update_pre_post_images(struct image *preimage,
struct image *postimage,
char *buf,
size_t len, size_t postlen)
char *buf, size_t len)
{
int i, ctx, reduced;
char *new_buf, *old_buf, *fixed;
struct image fixed_preimage = IMAGE_INIT;
size_t insert_pos = 0;
int i, ctx, reduced;
const char *fixed;

/*
* Update the preimage with whitespace fixes. Note that we
@ -2328,43 +2326,24 @@ static void update_pre_post_images(struct image *preimage,
* free "oldlines".
*/
image_prepare(&fixed_preimage, buf, len, 1);
assert(postlen
? fixed_preimage.line_nr == preimage->line_nr
: fixed_preimage.line_nr <= preimage->line_nr);
for (i = 0; i < fixed_preimage.line_nr; i++)
fixed_preimage.line[i].flag = preimage->line[i].flag;
free(preimage->line);
image_clear(preimage);
*preimage = fixed_preimage;
fixed = preimage->buf.buf;

/*
* Adjust the common context lines in postimage. This can be
* done in-place when we are shrinking it with whitespace
* fixing, but needs a new buffer when ignoring whitespace or
* expanding leading tabs to spaces.
*
* We trust the caller to tell us if the update can be done
* in place (postlen==0) or not.
* Adjust the common context lines in postimage.
*/
old_buf = postimage->buf;
if (postlen)
new_buf = postimage->buf = xmalloc(postlen);
else
new_buf = old_buf;
fixed = preimage->buf;

for (i = reduced = ctx = 0; i < postimage->line_nr; i++) {
size_t l_len = postimage->line[i].len;

if (!(postimage->line[i].flag & LINE_COMMON)) {
/* an added line -- no counterparts in preimage */
memmove(new_buf, old_buf, l_len);
old_buf += l_len;
new_buf += l_len;
insert_pos += l_len;
continue;
}

/* a common context -- skip it in the original postimage */
old_buf += l_len;

/* and find the corresponding one in the fixed preimage */
while (ctx < preimage->line_nr &&
!(preimage->line[ctx].flag & LINE_COMMON)) {
@ -2383,21 +2362,15 @@ static void update_pre_post_images(struct image *preimage,

/* and copy it in, while fixing the line length */
l_len = preimage->line[ctx].len;
memcpy(new_buf, fixed, l_len);
new_buf += l_len;
strbuf_splice(&postimage->buf, insert_pos, postimage->line[i].len,
fixed, l_len);
insert_pos += l_len;
fixed += l_len;
postimage->line[i].len = l_len;
ctx++;
}

if (postlen
? postlen < new_buf - postimage->buf
: postimage->len < new_buf - postimage->buf)
BUG("caller miscounted postlen: asked %d, orig = %d, used = %d",
(int)postlen, (int) postimage->len, (int)(new_buf - postimage->buf));

/* Fix the length of the whole thing */
postimage->len = new_buf - postimage->buf;
postimage->line_nr -= reduced;
}

@ -2447,7 +2420,6 @@ static int line_by_line_fuzzy_match(struct image *img,
int i;
size_t imgoff = 0;
size_t preoff = 0;
size_t postlen = postimage->len;
size_t extra_chars;
char *buf;
char *preimage_eof;
@ -2460,11 +2432,9 @@ static int line_by_line_fuzzy_match(struct image *img,
size_t prelen = preimage->line[i].len;
size_t imglen = img->line[current_lno+i].len;

if (!fuzzy_matchlines(img->buf + current + imgoff, imglen,
preimage->buf + preoff, prelen))
if (!fuzzy_matchlines(img->buf.buf + current + imgoff, imglen,
preimage->buf.buf + preoff, prelen))
return 0;
if (preimage->line[i].flag & LINE_COMMON)
postlen += imglen - prelen;
imgoff += imglen;
preoff += prelen;
}
@ -2480,10 +2450,10 @@ static int line_by_line_fuzzy_match(struct image *img,
* are whitespace characters. (This can only happen if
* we are removing blank lines at the end of the file.)
*/
buf = preimage_eof = preimage->buf + preoff;
buf = preimage_eof = preimage->buf.buf + preoff;
for ( ; i < preimage->line_nr; i++)
preoff += preimage->line[i].len;
preimage_end = preimage->buf + preoff;
preimage_end = preimage->buf.buf + preoff;
for ( ; buf < preimage_end; buf++)
if (!isspace(*buf))
return 0;
@ -2497,11 +2467,11 @@ static int line_by_line_fuzzy_match(struct image *img,
*/
extra_chars = preimage_end - preimage_eof;
strbuf_init(&fixed, imgoff + extra_chars);
strbuf_add(&fixed, img->buf + current, imgoff);
strbuf_add(&fixed, img->buf.buf + current, imgoff);
strbuf_add(&fixed, preimage_eof, extra_chars);
fixed_buf = strbuf_detach(&fixed, &fixed_len);
update_pre_post_images(preimage, postimage,
fixed_buf, fixed_len, postlen);
fixed_buf, fixed_len);
return 1;
}

@ -2517,7 +2487,8 @@ static int match_fragment(struct apply_state *state,
int i;
const char *orig, *target;
struct strbuf fixed = STRBUF_INIT;
size_t postlen;
char *fixed_buf;
size_t fixed_len;
int preimage_limit;
int ret;

@ -2573,9 +2544,9 @@ static int match_fragment(struct apply_state *state,
* exactly.
*/
if ((match_end
? (current + preimage->len == img->len)
: (current + preimage->len <= img->len)) &&
!memcmp(img->buf + current, preimage->buf, preimage->len)) {
? (current + preimage->buf.len == img->buf.len)
: (current + preimage->buf.len <= img->buf.len)) &&
!memcmp(img->buf.buf + current, preimage->buf.buf, preimage->buf.len)) {
ret = 1;
goto out;
}
@ -2589,7 +2560,7 @@ static int match_fragment(struct apply_state *state,
*/
const char *buf, *buf_end;

buf = preimage->buf;
buf = preimage->buf.buf;
buf_end = buf;
for (i = 0; i < preimage_limit; i++)
buf_end += preimage->line[i].len;
@ -2634,21 +2605,14 @@ static int match_fragment(struct apply_state *state,
* fixed.
*/

/* First count added lines in postimage */
postlen = 0;
for (i = 0; i < postimage->line_nr; i++) {
if (!(postimage->line[i].flag & LINE_COMMON))
postlen += postimage->line[i].len;
}

/*
* The preimage may extend beyond the end of the file,
* but in this loop we will only handle the part of the
* preimage that falls within the file.
*/
strbuf_grow(&fixed, preimage->len + 1);
orig = preimage->buf;
target = img->buf + current;
strbuf_grow(&fixed, preimage->buf.len + 1);
orig = preimage->buf.buf;
target = img->buf.buf + current;
for (i = 0; i < preimage_limit; i++) {
size_t oldlen = preimage->line[i].len;
size_t tgtlen = img->line[current_lno + i].len;
@ -2677,10 +2641,6 @@ static int match_fragment(struct apply_state *state,
!memcmp(tgtfix.buf, fixed.buf + fixstart,
fixed.len - fixstart));

/* Add the length if this is common with the postimage */
if (preimage->line[i].flag & LINE_COMMON)
postlen += tgtfix.len;

strbuf_release(&tgtfix);
if (!match) {
ret = 0;
@ -2722,10 +2682,9 @@ static int match_fragment(struct apply_state *state,
* has whitespace breakages unfixed, and fixing them makes the
* hunk match. Update the context lines in the postimage.
*/
if (postlen < postimage->len)
postlen = 0;
fixed_buf = strbuf_detach(&fixed, &fixed_len);
update_pre_post_images(preimage, postimage,
fixed.buf, fixed.len, postlen);
fixed_buf, fixed_len);

ret = 1;

@ -2839,6 +2798,7 @@ static void update_image(struct apply_state *state,
*/
int i, nr;
size_t remove_count, insert_count, applied_at = 0;
size_t result_alloc;
char *result;
int preimage_limit;

@ -2861,19 +2821,18 @@ static void update_image(struct apply_state *state,
remove_count = 0;
for (i = 0; i < preimage_limit; i++)
remove_count += img->line[applied_pos + i].len;
insert_count = postimage->len;
insert_count = postimage->buf.len;

/* Adjust the contents */
result = xmalloc(st_add3(st_sub(img->len, remove_count), insert_count, 1));
memcpy(result, img->buf, applied_at);
memcpy(result + applied_at, postimage->buf, postimage->len);
memcpy(result + applied_at + postimage->len,
img->buf + (applied_at + remove_count),
img->len - (applied_at + remove_count));
free(img->buf);
img->buf = result;
img->len += insert_count - remove_count;
result[img->len] = '\0';
result_alloc = st_add3(st_sub(img->buf.len, remove_count), insert_count, 1);
result = xmalloc(result_alloc);
memcpy(result, img->buf.buf, applied_at);
memcpy(result + applied_at, postimage->buf.buf, postimage->buf.len);
memcpy(result + applied_at + postimage->buf.len,
img->buf.buf + (applied_at + remove_count),
img->buf.len - (applied_at + remove_count));
strbuf_attach(&img->buf, result, postimage->buf.len + img->buf.len - remove_count,
result_alloc);

/* Adjust the line table */
nr = img->line_nr + postimage->line_nr - preimage_limit;
@ -3054,10 +3013,8 @@ static int apply_one_fragment(struct apply_state *state,
match_end = !state->unidiff_zero && !trailing;

pos = frag->newpos ? (frag->newpos - 1) : 0;
preimage.buf = oldlines;
preimage.len = old - oldlines;
postimage.buf = newlines.buf;
postimage.len = newlines.len;
strbuf_add(&preimage.buf, oldlines, old - oldlines);
strbuf_swap(&postimage.buf, &newlines);

for (;;) {

@ -3145,8 +3102,8 @@ static int apply_one_fragment(struct apply_state *state,
out:
free(oldlines);
strbuf_release(&newlines);
free(preimage.line);
free(postimage.line);
image_clear(&preimage);
image_clear(&postimage);

return (applied_pos < 0);
}
@ -3176,18 +3133,16 @@ static int apply_binary_fragment(struct apply_state *state,
}
switch (fragment->binary_patch_method) {
case BINARY_DELTA_DEFLATED:
dst = patch_delta(img->buf, img->len, fragment->patch,
dst = patch_delta(img->buf.buf, img->buf.len, fragment->patch,
fragment->size, &len);
if (!dst)
return -1;
image_clear(img);
img->buf = dst;
img->len = len;
strbuf_attach(&img->buf, dst, len, len + 1);
return 0;
case BINARY_LITERAL_DEFLATED:
image_clear(img);
img->len = fragment->size;
img->buf = xmemdupz(fragment->patch, img->len);
strbuf_add(&img->buf, fragment->patch, fragment->size);
return 0;
}
return -1;
@ -3223,8 +3178,8 @@ static int apply_binary(struct apply_state *state,
* See if the old one matches what the patch
* applies to.
*/
hash_object_file(the_hash_algo, img->buf, img->len, OBJ_BLOB,
&oid);
hash_object_file(the_hash_algo, img->buf.buf, img->buf.len,
OBJ_BLOB, &oid);
if (strcmp(oid_to_hex(&oid), patch->old_oid_prefix))
return error(_("the patch applies to '%s' (%s), "
"which does not match the "
@ -3233,7 +3188,7 @@ static int apply_binary(struct apply_state *state,
}
else {
/* Otherwise, the old one must be empty. */
if (img->len)
if (img->buf.len)
return error(_("the patch applies to an empty "
"'%s' but it is not empty"), name);
}
@ -3257,8 +3212,7 @@ static int apply_binary(struct apply_state *state,
"'%s' cannot be read"),
patch->new_oid_prefix, name);
image_clear(img);
img->buf = result;
img->len = size;
strbuf_attach(&img->buf, result, size, size + 1);
} else {
/*
* We have verified buf matches the preimage;
@ -3270,7 +3224,7 @@ static int apply_binary(struct apply_state *state,
name);

/* verify that the result matches */
hash_object_file(the_hash_algo, img->buf, img->len, OBJ_BLOB,
hash_object_file(the_hash_algo, img->buf.buf, img->buf.len, OBJ_BLOB,
&oid);
if (strcmp(oid_to_hex(&oid), patch->new_oid_prefix))
return error(_("binary patch to '%s' creates incorrect result (expecting %s, got %s)"),
@ -3540,14 +3494,14 @@ static int resolve_to(struct image *image, const struct object_id *result_id)
{
unsigned long size;
enum object_type type;
char *data;

image_clear(image);

image->buf = repo_read_object_file(the_repository, result_id, &type,
&size);
if (!image->buf || type != OBJ_BLOB)
data = repo_read_object_file(the_repository, result_id, &type, &size);
if (!data || type != OBJ_BLOB)
die("unable to read blob object %s", oid_to_hex(result_id));
image->len = size;
strbuf_attach(&image->buf, data, size, size + 1);

return 0;
}
@ -3589,8 +3543,7 @@ static int three_way_merge(struct apply_state *state,
return -1;
}
image_clear(image);
image->buf = result.ptr;
image->len = result.size;
strbuf_attach(&image->buf, result.ptr, result.size, result.size);

return status;
}
@ -3677,7 +3630,7 @@ static int try_threeway(struct apply_state *state,
return -1;
}
/* post_oid is theirs */
write_object_file(tmp_image.buf, tmp_image.len, OBJ_BLOB, &post_oid);
write_object_file(tmp_image.buf.buf, tmp_image.buf.len, OBJ_BLOB, &post_oid);
image_clear(&tmp_image);

/* our_oid is ours */
@ -3690,7 +3643,7 @@ static int try_threeway(struct apply_state *state,
return error(_("cannot read the current contents of '%s'"),
patch->old_name);
}
write_object_file(tmp_image.buf, tmp_image.len, OBJ_BLOB, &our_oid);
write_object_file(tmp_image.buf.buf, tmp_image.buf.len, OBJ_BLOB, &our_oid);
image_clear(&tmp_image);

/* in-core three-way merge between post and our using pre as base */
@ -3743,8 +3696,7 @@ static int apply_data(struct apply_state *state, struct patch *patch,
return -1;
}
}
patch->result = image.buf;
patch->resultsize = image.len;
patch->result = strbuf_detach(&image.buf, &patch->resultsize);
add_to_fn_table(state, patch);
free(image.line);


1
t/t3436-rebase-more-options.sh
View File

@ -5,6 +5,7 @@

test_description='tests to ensure compatibility between am and interactive backends'

TEST_PASSES_SANITIZE_LEAK=true
. ./test-lib.sh

. "$TEST_DIRECTORY"/lib-rebase.sh

4
t/t4107-apply-ignore-whitespace.sh
View File

@ -3,9 +3,9 @@
# Copyright (c) 2009 Giuseppe Bilotta
#

test_description='git-apply --ignore-whitespace.
test_description='git-apply --ignore-whitespace.'

'
TEST_PASSES_SANITIZE_LEAK=true
. ./test-lib.sh

# This primes main.c file that indents without using HT at all.

1
t/t4124-apply-ws-rule.sh
View File

@ -2,6 +2,7 @@

test_description='core.whitespace rules and git apply'

TEST_PASSES_SANITIZE_LEAK=true
. ./test-lib.sh

prepare_test_file () {

1
t/t4125-apply-ws-fuzz.sh
View File

@ -2,6 +2,7 @@

test_description='applying patch that has broken whitespaces in context'

TEST_PASSES_SANITIZE_LEAK=true
. ./test-lib.sh

test_expect_success setup '

1
t/t4138-apply-ws-expansion.sh
View File

@ -5,6 +5,7 @@

test_description='git apply test patches with whitespace expansion.'

TEST_PASSES_SANITIZE_LEAK=true
. ./test-lib.sh

test_expect_success setup '