Fix implicit sign conversion in projection code

Author: joto

src/reprojection.cpp

@@ -9,6 +9,7 @@
 
 #include <osmium/geom/mercator_projection.hpp>
 
+#include "format.hpp"
 #include "reprojection.hpp"
 
 namespace {
@@ -82,5 +83,9 @@ std::shared_ptr<reprojection> reprojection::create_projection(int srs)
         break;
     }
 
+    if (srs <= 0) {
+        throw std::runtime_error{"Invalid projection SRID '{}'."_format(srs)};
+    }
+
     return make_generic_projection(srs);
 }

src/wkb.hpp

@@ -102,7 +102,10 @@ inline std::string create_point(double x, double y, uint32_t srid = 4326)
 class writer_t
 {
 public:
-    explicit writer_t(uint32_t srid) : m_srid(srid) {}
+    explicit writer_t(int srid) : m_srid(static_cast<uint32_t>(srid))
+    {
+        assert(srid > 0);
+    }
 
     void add_sub_geometry(std::string const &part)
     {