Improve error message

Re GH #1912

1 files changed, 5 insertions, 3 deletions

diff --git a/src/lib/base/scan_name.cpp b/src/lib/base/scan_name.cpp
index 8a20caddb..954db7c45 100644
--- a/src/lib/base/scan_name.cpp
+++ b/src/lib/base/scan_name.cpp
@@ -13,8 +13,7 @@ namespace Botan {
 
 namespace {
 
-std::string make_arg(
-   const std::vector<std::pair<size_t, std::string> >& name, size_t start)
+std::string make_arg(const std::vector<std::pair<size_t, std::string>>& name, size_t start)
    {
    std::string output = name[start].second;
    size_t level = name[start].first;
@@ -60,7 +59,10 @@ SCAN_Name::SCAN_Name(const char* algo_spec) : SCAN_Name(std::string(algo_spec))
 
 SCAN_Name::SCAN_Name(std::string algo_spec) : m_orig_algo_spec(algo_spec), m_alg_name(), m_args(), m_mode_info()
    {
-   std::vector<std::pair<size_t, std::string> > name;
+   if(algo_spec.size() == 0)
+      throw Invalid_Argument("Expected algorithm name, got empty string");
+
+   std::vector<std::pair<size_t, std::string>> name;
    size_t level = 0;
    std::pair<size_t, std::string> accum = std::make_pair(level, "");