xavi
/
dynstr
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Fix lifetime issues with va_list 

The standard requires both va_start and va_end to be called from the
same function. On the other hand, vsnprintf and vsprintf leave the
va_list on an undefined state according to the standard, so a copy must
be created before a second call to these functions.
This commit is contained in:
Xavier Del Campo Romero 2020-10-14 08:27:19 +02:00
parent 837c9427de
commit 601a813325
1 changed files with 53 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

87
dynstr.c
View File

@ -33,73 +33,92 @@ void dynstr_init(struct dynstr *const d)
enum dynstr_err dynstr_vappend(struct dynstr *const d, const char *const format, va_list ap) enum dynstr_err dynstr_vappend(struct dynstr *const d, const char *const format, va_list ap)
{ {
enum dynstr_err err = DYNSTR_OK; enum dynstr_err err = DYNSTR_OK;
const size_t src_len = vsnprintf(NULL, 0, format, ap); va_list apc;
const size_t new_len = d->len + src_len + 1;
d->str = realloc(d->str, new_len * sizeof *d->str); va_copy(apc, ap);
if (d->str)
{ {
vsprintf(d->str + d->len, format, ap); const size_t src_len = vsnprintf(NULL, 0, format, ap);
d->len += src_len; const size_t new_len = d->len + src_len + 1;
}
else d->str = realloc(d->str, new_len * sizeof *d->str);
{
err = DYNSTR_ERR_ALLOC; if (d->str)
{
vsprintf(d->str + d->len, format, apc);
d->len += src_len;
}
else
{
err = DYNSTR_ERR_ALLOC;
}
} }
va_end(ap); va_end(apc);
return err; return err;
} }
enum dynstr_err dynstr_append(struct dynstr *const d, const char *const format, ...) enum dynstr_err dynstr_append(struct dynstr *const d, const char *const format, ...)
{ {
va_list ap; va_list ap;
enum dynstr_err err;
va_start(ap, format); va_start(ap, format);
return dynstr_vappend(d, format, ap); err = dynstr_vappend(d, format, ap);
va_end(ap);
return err;
} }
enum dynstr_err dynstr_vprepend(struct dynstr *const d, const char *const format, va_list ap) enum dynstr_err dynstr_vprepend(struct dynstr *const d, const char *const format, va_list ap)
{ {
const size_t src_len = vsnprintf(NULL, 0, format, ap); enum dynstr_err err = DYNSTR_OK;
const size_t new_len = d->len + src_len + 1; va_list apc;
d->str = realloc(d->str, new_len * sizeof *d->str); va_copy(apc, ap);
if (d->str && d->len)
{ {
/* Keep byte that will be removed by later call to vsprintf. */ const size_t src_len = vsnprintf(NULL, 0, format, ap);
const char c = *d->str; const size_t new_len = d->len + src_len + 1;
for (size_t i = new_len - 1, j = d->len; j <= d->len; i--, j--) d->str = realloc(d->str, new_len * sizeof *d->str);
if (d->str && d->len)
{ {
d->str[i] = d->str[j]; /* Keep byte that will be removed by later call to vsprintf. */
const char c = *d->str;
for (size_t i = new_len - 1, j = d->len; j <= d->len; i--, j--)
{
d->str[i] = d->str[j];
}
vsprintf(d->str, format, apc);
d->str[src_len] = c;
}
else if (!d->len)
{
vsprintf(d->str + d->len, format, apc);
}
else
{
err = DYNSTR_ERR_ALLOC;
} }
vsprintf(d->str, format, ap); d->len += src_len;
d->str[src_len] = c;
}
else if (!d->len)
{
vsprintf(d->str + d->len, format, ap);
}
else
{
return DYNSTR_ERR_ALLOC;
} }
va_end(ap); va_end(apc);
d->len += src_len; return err;
return DYNSTR_OK;
} }
enum dynstr_err dynstr_prepend(struct dynstr *const d, const char *const format, ...) enum dynstr_err dynstr_prepend(struct dynstr *const d, const char *const format, ...)
{ {
va_list ap; va_list ap;
enum dynstr_err err;
va_start(ap, format); va_start(ap, format);
return dynstr_vprepend(d, format, ap); err = dynstr_vprepend(d, format, ap);
return err;
} }
enum dynstr_err dynstr_dup(struct dynstr *const dst, const struct dynstr *const src) enum dynstr_err dynstr_dup(struct dynstr *const dst, const struct dynstr *const src)