Check return value of `vasprintf` and `asprintf`

According to `man asprintf`, leaving these return value unchecked is dangerous:

> If memory allocation wasn't possible, or some other error occurs, these functions will return -1, and the contents of strp are undefined.

```C
#define _GNU_SOURCE /* See feature_test_macros(7)*/
#include

int asprintf(char **strp, const char *fmt, ...);
int vasprintf(char **strp, const char *fmt, va_list ap);

```
It does fail for various reasons, e.g. EILSEQ ( A wide-character code that does not correspond to a valid character has been detected.)
https://pubs.opengroup.org/onlinepubs/9699919799/functions/fprintf.html

An example is given by https://stackoverflow.com/questions/65334245/what-is-an-encoding-error-for-sprintf-that-should-return-1:

```C
char buf[42];
wchar_t s[] = { 0xFFFF,49,50,51,0 };
int i = snprintf(buf, sizeof buf, "<%ls>", s);
printf("%d\n", i);
```

`asprintf` is used extensively in various modules, we need to check its usage carefully.