fix odr test for bundled boost and test this

.travis.yml

@@ -70,6 +70,9 @@ matrix:
         # prepare build
         - ./bootstrap.sh
         - ./b2 headers
+        # simulate bundled boost by moving the headers instead of symlinking
+        - rm -rf boost/histogram.pp boost/histogram
+        - mv -f libs/histogram/include/boost/* boost
         - cd libs/histogram
         - B2="../../b2 -q -j2 warnings-as-errors=on"
 

test/check_odr_test.py

@@ -4,6 +4,10 @@
 # (See accompanying file LICENSE_1_0.txt
 # or copy at http://www.boost.org/LICENSE_1_0.txt)
 
+"""
+This test makes sure that all boost.histogram headers are included in the ODR test carried out in odr_main_test.cpp. See that file for details on why this test needed.
+"""
+
 import os
 import sys
 import re
@@ -11,12 +15,20 @@ import re
 this_path = os.path.dirname(__file__)
 
 all_headers = set()
-include_path = os.path.join(this_path, "..", "include")
+# Includes are either in this_path/../include for the standalone version or ...
+include_path = os.path.join(this_path, "..", "include", "boost", "histogram")
+if not os.path.exists(include_path):
+    # ... in this_path/../../.. for the bundled boost release
+    include_path = os.path.join(this_path, "..", "..", "..", "boost", "histogram")
+    assert os.path.exists(include_path)
+
+# this has to be rindex, because any leading path could also be called boost
+root_include_path = include_path[: include_path.rindex("boost")]
+
 for root, dirs, files in os.walk(include_path):
     for fn in files:
         fn = os.path.join(root, fn)
-        assert fn.startswith(include_path)
-        fn = fn[len(include_path) + 1 :]
+        fn = fn[len(root_include_path) :]
         all_headers.add(fn)
 
 
@@ -37,7 +49,7 @@ while unread_headers:
     included_headers.update(unread_headers)
     for hdr in tuple(unread_headers):  # copy needed because unread_headers is modified
         unread_headers.remove(hdr)
-        for hdr2 in get_headers(os.path.join(include_path, hdr)):
+        for hdr2 in get_headers(os.path.join(root_include_path, hdr)):
             if hdr2 not in included_headers:
                 unread_headers.add(hdr2)
 

test/odr_main_test.cpp

@@ -4,7 +4,18 @@
 // (See accompanying file LICENSE_1_0.txt
 // or copy at http://www.boost.org/LICENSE_1_0.txt)
 
-// include all headers again
+/*
+  For a header-only library, it is important to not accidentally violate the
+  One-Definition-Rule (ODR), which causes linker errors. The ODR is violated
+  when a non-templated function declared in a header is not inlined, and that
+  header is then included in several translation units which are then linked
+  together.
+
+  We carry out this test by including all headers in two separate translation
+  units which are then linked together. There is an additional test called
+  check_odr_test.py which checks that "odr_test.cpp" includes all headers.
+*/
+
 #include "odr_test.cpp"
 
 int main() { return 0; }

test/odr_test.cpp

@@ -4,9 +4,7 @@
 // (See accompanying file LICENSE_1_0.txt
 // or copy at http://www.boost.org/LICENSE_1_0.txt)
 
-// include all Boost.Histogram header here
+// include all Boost.Histogram header here; see odr_main_test.cpp for details
 #include <boost/histogram.hpp>
-#include <boost/histogram/accumulators.hpp>
-#include <boost/histogram/axis/ostream.hpp>
 #include <boost/histogram/ostream.hpp>
 #include <boost/histogram/serialization.hpp>