Make float database operations more consistent.

We don't use floats in GnuCash, we use doubles (and those as little as
possible), but dbd-sqlite3 is broken in that it stores only floats.
Simply casting floats to doubles introduces bogus additional digits
that can cause round-trip tests to fail. Instead convert floats to
doubles by multiplying by 10E6, rounding, then dividing by 10E6.

libgnucash/backend/dbi/gnc-dbisqlresult.cpp

@@ -30,6 +30,7 @@ extern "C"
 /* For direct access to dbi data structs, sadly needed for datetime */
 #include <dbi/dbi-dev.h>
 }
+#include <cmath>
 #include <gnc-datetime.hpp>
 #include "gnc-dbisqlresult.hpp"
 #include "gnc-dbisqlconnection.hpp"
@@ -109,7 +110,7 @@ GncDbiSqlResult::IteratorImpl::get_int_at_col(const char* col) const
     return dbi_result_get_longlong (m_inst->m_dbi_result, col);
 }
 
-float
+double
 GncDbiSqlResult::IteratorImpl::get_float_at_col(const char* col) const
 {
     auto type = dbi_result_get_field_type (m_inst->m_dbi_result, col);
@@ -118,8 +119,9 @@ GncDbiSqlResult::IteratorImpl::get_float_at_col(const char* col) const
        (attrs & DBI_DECIMAL_SIZEMASK) != DBI_DECIMAL_SIZE4)
         throw (std::invalid_argument{"Requested float from non-float column."});
     auto locale = gnc_push_locale (LC_NUMERIC, "C");
-    auto retval =  dbi_result_get_float(m_inst->m_dbi_result, col);
+    auto interim =  dbi_result_get_float(m_inst->m_dbi_result, col);
     gnc_pop_locale (LC_NUMERIC, locale);
+    double retval = static_cast<double>(round(interim * 1000000.0)) / 1000000.0;
     return retval;
 }
 

libgnucash/backend/dbi/gnc-dbisqlresult.hpp

@@ -54,7 +54,7 @@ protected:
         virtual GncSqlRow& operator++(int) { return ++(*this); };
         virtual GncSqlResult* operator*() { return m_inst; }
         virtual int64_t get_int_at_col (const char* col) const;
-        virtual float get_float_at_col (const char* col) const;
+        virtual double get_float_at_col (const char* col) const;
         virtual double get_double_at_col (const char* col) const;
         virtual std::string get_string_at_col (const char* col)const;
         virtual time64 get_time64_at_col (const char* col) const;

libgnucash/backend/sql/gnc-sql-column-table-entry.cpp

@@ -283,7 +283,7 @@ GncSqlColumnTableEntryImpl<CT_DOUBLE>::load (const GncSqlBackend* sql_be,
     {
         try
         {
-            val = static_cast<double>(row.get_float_at_col(m_col_name));
+            val = row.get_float_at_col(m_col_name);
         }
         catch (std::invalid_argument&)
         {

libgnucash/backend/sql/gnc-sql-result.hpp

@@ -52,7 +52,7 @@ protected:
         virtual GncSqlRow& operator++() = 0;
         virtual GncSqlResult* operator*() = 0;
         virtual int64_t get_int_at_col (const char* col) const = 0;
-        virtual float get_float_at_col (const char* col) const = 0;
+        virtual double get_float_at_col (const char* col) const = 0;
         virtual double get_double_at_col (const char* col) const = 0;
         virtual std::string get_string_at_col (const char* col) const = 0;
         virtual time64 get_time64_at_col (const char* col) const = 0;
@@ -88,7 +88,7 @@ public:
     friend bool operator!=(const GncSqlRow&, const GncSqlRow&);
     int64_t get_int_at_col (const char* col) const {
         return m_iter->get_int_at_col (col); }
-    float get_float_at_col (const char* col) const {
+    double get_float_at_col (const char* col) const {
         return m_iter->get_float_at_col (col); }
     double get_double_at_col (const char* col) const {
         return m_iter->get_double_at_col (col); }

libgnucash/backend/sql/test/utest-gnc-backend-sql.cpp

@@ -66,7 +66,7 @@ protected:
             virtual GncSqlResult* operator*() { return m_inst; }
             virtual int64_t get_int_at_col (const char* col) const
             { return 1LL; }
-            virtual float get_float_at_col (const char* col) const
+            virtual double get_float_at_col (const char* col) const
             { return 1.0; }
             virtual double get_double_at_col (const char* col) const
             { return 1.0; }