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dynstr.c: Fix memory leak if realloc(3) fails 

According to C99 §7.20.3.4:

If memory for the new object cannot be allocated, the old object is not
deallocated and its value is unchanged.

Therefore, a temporary pointer must be used to ensure the original
object can still be deallocated should realloc(3) return a null pointer.
This commit is contained in:
Xavier Del Campo Romero 2023-03-08 01:21:16 +01:00
parent 8e7557ef7a
commit 909d716a1e
1 changed files with 17 additions and 15 deletions
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32
dynstr.c
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@ -40,13 +40,13 @@ enum dynstr_err dynstr_vappend(struct dynstr *const d, const char *const format,
{
const size_t src_len = vsnprintf(NULL, 0, format, ap);
const size_t new_len = d->len + src_len + 1;
char *const s = realloc(d->str, new_len * sizeof *d->str);
d->str = realloc(d->str, new_len * sizeof *d->str);
if (d->str)
if (s)
{
vsprintf(d->str + d->len, format, apc);
vsprintf(s + d->len, format, apc);
d->len += src_len;
d->str = s;
}
else
{
@ -79,25 +79,26 @@ enum dynstr_err dynstr_vprepend(struct dynstr *const d, const char *const format
{
const size_t src_len = vsnprintf(NULL, 0, format, ap);
const size_t new_len = d->len + src_len + 1;
char *const s = realloc(d->str, new_len * sizeof *d->str);
d->str = realloc(d->str, new_len * sizeof *d->str);
if (d->str && d->len)
if (s && d->len)
{
/* Keep byte that will be removed by later call to vsprintf. */
const char c = *d->str;
const char c = *s;
for (size_t i = new_len - 1, j = d->len; j <= d->len; i--, j--)
{
d->str[i] = d->str[j];
s[i] = s[j];
}
vsprintf(d->str, format, apc);
d->str[src_len] = c;
vsprintf(s, format, apc);
s[src_len] = c;
d->str = s;
}
else if (!d->len)
{
vsprintf(d->str + d->len, format, apc);
vsprintf(s + d->len, format, apc);
d->str = s;
}
else
{
@ -128,12 +129,13 @@ enum dynstr_err dynstr_dup(struct dynstr *const dst, const struct dynstr *const
if (src->len && src->str)
{
const size_t sz = (src->len + 1) * sizeof *dst->str;
dst->str = realloc(dst->str, sz);
char *const s = realloc(dst->str, sz);
if (dst->str)
if (s)
{
memcpy(dst->str, src->str, sz);
memcpy(s, src->str, sz);
dst->len = src->len;
dst->str = s;
}
else
{