git/xdiff-interface.c
Jeff King 3cd309c16f xdiff: avoid computing non-zero offset from NULL pointer
As with the previous commit, clang-11's UBSan complains about computing
offsets from a NULL pointer, causing some tests to fail. In this case,
though, we're actually computing a non-zero offset, which is even more
dubious. From t7810:

  xdiff-interface.c:268:14: runtime error: applying non-zero offset 1 to null pointer
  ...
  not ok 131 - grep -p with userdiff

The problem is our parsing of the funcname config. We count the number
of lines in the string, allocate an array, and then loop over our
allocated entries, parsing each line and moving our cursor to one past
the trailing newline for the next iteration.

But the final line will not generally have a trailing newline (since
it's a config value), and hence we go to one past NULL. In practice this
is OK, since our loop should terminate before we look at the value. But
even computing such an invalid pointer technically violates the
standard.

We can fix it by leaving the pointer at NULL if we're at the end, rather
than one-past. And while we're thinking about it, we can also document
the variant by asserting that our initial line-count matches the
second-pass of parsing.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-01-28 23:13:25 -08:00

324 lines
7.5 KiB
C

#include "cache.h"
#include "config.h"
#include "object-store.h"
#include "xdiff-interface.h"
#include "xdiff/xtypes.h"
#include "xdiff/xdiffi.h"
#include "xdiff/xemit.h"
#include "xdiff/xmacros.h"
#include "xdiff/xutils.h"
struct xdiff_emit_state {
xdiff_emit_hunk_fn hunk_fn;
xdiff_emit_line_fn line_fn;
void *consume_callback_data;
struct strbuf remainder;
};
static int xdiff_out_hunk(void *priv_,
long old_begin, long old_nr,
long new_begin, long new_nr,
const char *func, long funclen)
{
struct xdiff_emit_state *priv = priv_;
if (priv->remainder.len)
BUG("xdiff emitted hunk in the middle of a line");
priv->hunk_fn(priv->consume_callback_data,
old_begin, old_nr, new_begin, new_nr,
func, funclen);
return 0;
}
static void consume_one(void *priv_, char *s, unsigned long size)
{
struct xdiff_emit_state *priv = priv_;
char *ep;
while (size) {
unsigned long this_size;
ep = memchr(s, '\n', size);
this_size = (ep == NULL) ? size : (ep - s + 1);
priv->line_fn(priv->consume_callback_data, s, this_size);
size -= this_size;
s += this_size;
}
}
static int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf)
{
struct xdiff_emit_state *priv = priv_;
int i;
if (!priv->line_fn)
return 0;
for (i = 0; i < nbuf; i++) {
if (mb[i].ptr[mb[i].size-1] != '\n') {
/* Incomplete line */
strbuf_add(&priv->remainder, mb[i].ptr, mb[i].size);
continue;
}
/* we have a complete line */
if (!priv->remainder.len) {
consume_one(priv, mb[i].ptr, mb[i].size);
continue;
}
strbuf_add(&priv->remainder, mb[i].ptr, mb[i].size);
consume_one(priv, priv->remainder.buf, priv->remainder.len);
strbuf_reset(&priv->remainder);
}
if (priv->remainder.len) {
consume_one(priv, priv->remainder.buf, priv->remainder.len);
strbuf_reset(&priv->remainder);
}
return 0;
}
/*
* Trim down common substring at the end of the buffers,
* but end on a complete line.
*/
static void trim_common_tail(mmfile_t *a, mmfile_t *b)
{
const int blk = 1024;
long trimmed = 0, recovered = 0;
char *ap = a->size ? a->ptr + a->size : a->ptr;
char *bp = b->size ? b->ptr + b->size : b->ptr;
long smaller = (a->size < b->size) ? a->size : b->size;
while (blk + trimmed <= smaller && !memcmp(ap - blk, bp - blk, blk)) {
trimmed += blk;
ap -= blk;
bp -= blk;
}
while (recovered < trimmed)
if (ap[recovered++] == '\n')
break;
a->size -= trimmed - recovered;
b->size -= trimmed - recovered;
}
int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *xecb)
{
mmfile_t a = *mf1;
mmfile_t b = *mf2;
if (mf1->size > MAX_XDIFF_SIZE || mf2->size > MAX_XDIFF_SIZE)
return -1;
if (!xecfg->ctxlen && !(xecfg->flags & XDL_EMIT_FUNCCONTEXT))
trim_common_tail(&a, &b);
return xdl_diff(&a, &b, xpp, xecfg, xecb);
}
void discard_hunk_line(void *priv,
long ob, long on, long nb, long nn,
const char *func, long funclen)
{
}
int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
xdiff_emit_hunk_fn hunk_fn,
xdiff_emit_line_fn line_fn,
void *consume_callback_data,
xpparam_t const *xpp, xdemitconf_t const *xecfg)
{
int ret;
struct xdiff_emit_state state;
xdemitcb_t ecb;
memset(&state, 0, sizeof(state));
state.hunk_fn = hunk_fn;
state.line_fn = line_fn;
state.consume_callback_data = consume_callback_data;
memset(&ecb, 0, sizeof(ecb));
if (hunk_fn)
ecb.out_hunk = xdiff_out_hunk;
ecb.out_line = xdiff_outf;
ecb.priv = &state;
strbuf_init(&state.remainder, 0);
ret = xdi_diff(mf1, mf2, xpp, xecfg, &ecb);
strbuf_release(&state.remainder);
return ret;
}
int read_mmfile(mmfile_t *ptr, const char *filename)
{
struct stat st;
FILE *f;
size_t sz;
if (stat(filename, &st))
return error_errno("Could not stat %s", filename);
if ((f = fopen(filename, "rb")) == NULL)
return error_errno("Could not open %s", filename);
sz = xsize_t(st.st_size);
ptr->ptr = xmalloc(sz ? sz : 1);
if (sz && fread(ptr->ptr, sz, 1, f) != 1) {
fclose(f);
return error("Could not read %s", filename);
}
fclose(f);
ptr->size = sz;
return 0;
}
void read_mmblob(mmfile_t *ptr, const struct object_id *oid)
{
unsigned long size;
enum object_type type;
if (oideq(oid, &null_oid)) {
ptr->ptr = xstrdup("");
ptr->size = 0;
return;
}
ptr->ptr = read_object_file(oid, &type, &size);
if (!ptr->ptr || type != OBJ_BLOB)
die("unable to read blob object %s", oid_to_hex(oid));
ptr->size = size;
}
#define FIRST_FEW_BYTES 8000
int buffer_is_binary(const char *ptr, unsigned long size)
{
if (FIRST_FEW_BYTES < size)
size = FIRST_FEW_BYTES;
return !!memchr(ptr, 0, size);
}
struct ff_regs {
int nr;
struct ff_reg {
regex_t re;
int negate;
} *array;
};
static long ff_regexp(const char *line, long len,
char *buffer, long buffer_size, void *priv)
{
struct ff_regs *regs = priv;
regmatch_t pmatch[2];
int i;
int result;
/* Exclude terminating newline (and cr) from matching */
if (len > 0 && line[len-1] == '\n') {
if (len > 1 && line[len-2] == '\r')
len -= 2;
else
len--;
}
for (i = 0; i < regs->nr; i++) {
struct ff_reg *reg = regs->array + i;
if (!regexec_buf(&reg->re, line, len, 2, pmatch, 0)) {
if (reg->negate)
return -1;
break;
}
}
if (regs->nr <= i)
return -1;
i = pmatch[1].rm_so >= 0 ? 1 : 0;
line += pmatch[i].rm_so;
result = pmatch[i].rm_eo - pmatch[i].rm_so;
if (result > buffer_size)
result = buffer_size;
while (result > 0 && (isspace(line[result - 1])))
result--;
memcpy(buffer, line, result);
return result;
}
void xdiff_set_find_func(xdemitconf_t *xecfg, const char *value, int cflags)
{
int i;
struct ff_regs *regs;
xecfg->find_func = ff_regexp;
regs = xecfg->find_func_priv = xmalloc(sizeof(struct ff_regs));
for (i = 0, regs->nr = 1; value[i]; i++)
if (value[i] == '\n')
regs->nr++;
ALLOC_ARRAY(regs->array, regs->nr);
for (i = 0; i < regs->nr; i++) {
struct ff_reg *reg = regs->array + i;
const char *ep, *expression;
char *buffer = NULL;
if (!value)
BUG("mismatch between line count and parsing");
ep = strchr(value, '\n');
reg->negate = (*value == '!');
if (reg->negate && i == regs->nr - 1)
die("Last expression must not be negated: %s", value);
if (*value == '!')
value++;
if (ep)
expression = buffer = xstrndup(value, ep - value);
else
expression = value;
if (regcomp(&reg->re, expression, cflags))
die("Invalid regexp to look for hunk header: %s", expression);
free(buffer);
value = ep ? ep + 1 : NULL;
}
}
void xdiff_clear_find_func(xdemitconf_t *xecfg)
{
if (xecfg->find_func) {
int i;
struct ff_regs *regs = xecfg->find_func_priv;
for (i = 0; i < regs->nr; i++)
regfree(&regs->array[i].re);
free(regs->array);
free(regs);
xecfg->find_func = NULL;
xecfg->find_func_priv = NULL;
}
}
unsigned long xdiff_hash_string(const char *s, size_t len, long flags)
{
return xdl_hash_record(&s, s + len, flags);
}
int xdiff_compare_lines(const char *l1, long s1,
const char *l2, long s2, long flags)
{
return xdl_recmatch(l1, s1, l2, s2, flags);
}
int git_xmerge_style = -1;
int git_xmerge_config(const char *var, const char *value, void *cb)
{
if (!strcmp(var, "merge.conflictstyle")) {
if (!value)
die("'%s' is not a boolean", var);
if (!strcmp(value, "diff3"))
git_xmerge_style = XDL_MERGE_DIFF3;
else if (!strcmp(value, "merge"))
git_xmerge_style = 0;
/*
* Please update _git_checkout() in
* git-completion.bash when you add new merge config
*/
else
die("unknown style '%s' given for '%s'",
value, var);
return 0;
}
return git_default_config(var, value, cb);
}