[lmi-commits] [lmi] master 25212df 3/4: Make the just-added data members const

[Greg Chicares]

branch: master
commit 25212dfa442328f1d38755eb602c3886498a0e68
Author: Gregory W. Chicares <address@hidden>
Commit: Gregory W. Chicares <address@hidden>

    Make the just-added data members const
    
    See the immediately preceding commit.
    
    This commit recovers the constness of the penultimate revision, which
    is great. And it initializes const members in the ctor-initializer,
    which is fine (and necessary). But it introduces a latent defect--if
    the newly-added unit test is not commented out, then this line:
        ,groups_per_page_    {(max_lines_per_page_ + 1) / lines_per_group_}
    results in:
      Unhandled exception: divide by zero
    That problem had previously been precluded by assertions in the body
    of the ctor. Now, the assertions come too late: the body isn't reached
    because a fault occurs in the ctor-initializer.
---
 report_table.cpp      | 13 +++++--------
 report_table.hpp      |  8 ++++----
 report_table_test.cpp |  9 +++++++++
 3 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/report_table.cpp b/report_table.cpp
index 91e7651..5a55979 100644
--- a/report_table.cpp
+++ b/report_table.cpp
@@ -181,6 +181,11 @@ paginator::paginator(int total_rows, int rows_per_group, 
int max_lines_per_page)
     :total_rows_         {total_rows}
     ,rows_per_group_     {rows_per_group}
     ,max_lines_per_page_ {max_lines_per_page}
+    // "+ 1": blank-line separator after each group.
+    ,lines_per_group_    {rows_per_group_ + 1}
+    // "+ 1": no blank-line separator after the last group.
+    ,groups_per_page_    {(max_lines_per_page_ + 1) / lines_per_group_}
+    ,rows_per_page_      {rows_per_group_ * groups_per_page_}
     ,page_count_         {1}
 {
     LMI_ASSERT(0 <= total_rows_);
@@ -194,14 +199,6 @@ paginator::paginator(int total_rows, int rows_per_group, 
int max_lines_per_page)
         return;
         }
 
-    // "+ 1": blank-line separator after each group.
-    lines_per_group_ = rows_per_group_ + 1;
-
-    // "+ 1": no blank-line separator after the last group.
-    groups_per_page_ = (max_lines_per_page_ + 1) / lines_per_group_;
-
-    rows_per_page_ = rows_per_group_ * groups_per_page_;
-
     page_count_ = outward_quotient(total_rows_, rows_per_page_);
 
     // Avoid widowing a partial group on the last page, by moving it
diff --git a/report_table.hpp b/report_table.hpp
index ace4c2b..b548cf2 100644
--- a/report_table.hpp
+++ b/report_table.hpp
@@ -148,10 +148,10 @@ class LMI_SO paginator
     int const max_lines_per_page_;
 
     // Internals in dependency order.
-    int /* const */ lines_per_group_;
-    int /* const */ groups_per_page_;
-    int /* const */ rows_per_page_;
-    int page_count_;
+    int const lines_per_group_;
+    int const groups_per_page_;
+    int const rows_per_page_;
+    int       page_count_;
 };
 
 #endif // report_table_hpp
diff --git a/report_table_test.cpp b/report_table_test.cpp
index 2c4f5e0..68f7e7e 100644
--- a/report_table_test.cpp
+++ b/report_table_test.cpp
@@ -439,6 +439,15 @@ void report_table_test::test_paginator()
         ,lmi_test::what_regex("^Assertion.*failed")
         );
 
+    // Negative number of rows per group.
+#if 0
+    BOOST_TEST_THROW
+        (paginator(1, -1, 1)
+        ,std::runtime_error
+        ,lmi_test::what_regex("^Assertion.*failed")
+        );
+#endif // 0
+
     // Insufficient room to print even one group.
     BOOST_TEST_THROW
         (paginator(1, 7, 3)