Detect when switches are specified more than once

Fixes #1219

1 files changed, 6 insertions, 0 deletions

diff --git a/src/parameters_parser.cc b/src/parameters_parser.cc
index 68a497c9..30154483 100644
--- a/src/parameters_parser.cc
+++ b/src/parameters_parser.cc
@@ -19,6 +19,7 @@ ParametersParser::ParametersParser(ParameterList params,
       m_desc(desc)
 {
     bool only_pos = desc.flags & ParameterDesc::Flags::SwitchesAsPositional;
+    Vector<bool> switch_seen(desc.switches.size(), false);
     for (size_t i = 0; i < params.size(); ++i)
     {
         if (not only_pos and params[i] == "--")
@@ -29,6 +30,11 @@ ParametersParser::ParametersParser(ParameterList params,
             if (it == m_desc.switches.end())
                 throw unknown_option(params[i]);
 
+            auto switch_index = it - m_desc.switches.begin();
+            if (switch_seen[switch_index])
+                throw runtime_error{format("switch '-{}' specified more than once", it->key)};
+            switch_seen[switch_index] = true;
+
             if (it->value.takes_arg)
             {
                 ++i;