FP_CTX_MAGIC
MUST_HAVE(((in != NULL) && (in->magic == FP_MAGIC) && (in->ctx != NULL) && (in->ctx->magic == FP_CTX_MAGIC)), ret, err);
MUST_HAVE(((ctx != NULL) && (ctx->magic == FP_CTX_MAGIC)), ret, err);
ctx->magic = FP_CTX_MAGIC;