I'm sure the sizes are wrong, but this caused a core dump:
Algo name is SHA256
Ohhhh jeeee: ... this is a bug (md.c:809:md_read)
Aborted (core dumped)

I created a hash algorithm with:
gcry_md_open(&hd, GCRY_MD_SHA256, GCRY_MD_FLAG_SECURE);

I then performed a read an SHA1 (not SHA256) in an invalid manner:
printf("Hashed value is %s\n", gcry_md_read(hd, GCRY_MD_SHA1));