Configuring with --with-apr=/usr usually fails. This is because:

The generated exports.c #includes all *.h files found in <apr-prefix>/include
If <apr-prefix> == /usr , then this means /usr/include/*.h !!!

On most systems, it's quite likely that some of these are C++ headers, or have
conflicting definitions, so breaking the build.

The solution is to only include apr and apr-util headers from the apr and
apr-util include directories. This is easy to do, as apr and apr-util headers
follow a consistent naming scheme.

Here is a patch, to include only apr.h, apu.h, apr_*.h, and apu_*.h from the apr
and apr-util include directories.

It is against httpd-2.0.49 (current release), but it applies without conflict to
 current 2.0-HEAD and 2.1-HEAD.

--- httpd-2.0.49/server/Makefile.in.orig 2004-06-21 01:00:42.308012800 +0100
+++ httpd-2.0.49/server/Makefile.in 2004-06-21 01:14:25.131174400 +0100
@@ -31,7 +31,8 @@
 
 util.lo: test_char.h
 
-EXPORT_DIRS = $(top_srcdir)/include $(top_srcdir)/os/$(OS_DIR)
$(APR_INCLUDEDIR) $(APU_INCLUDEDIR) $(top_srcdir)/modules/http
+EXPORT_DIRS = $(top_srcdir)/include $(top_srcdir)/os/$(OS_DIR)
$(top_srcdir)/modules/http
+EXPORT_DIRS_APR = $(APR_INCLUDEDIR) $(APU_INCLUDEDIR)
 
 # If export_files is a dependency here, but we remove it during this stage,
 # when exports.c is generated, make will not detect that export_files is no
@@ -58,6 +59,10 @@
  for dir in $(EXPORT_DIRS); do \
      ls $$dir/*.h >> $$tmp; \
  done; \
+ for dir in $(EXPORT_DIRS_APR); do \
+     ls $$dir/ap[ru].h >> $$tmp 2>/dev/null; \
+     ls $$dir/ap[ru]_*.h >> $$tmp 2>/dev/null; \
+ done; \
  sort -u $$tmp > $@; \
  rm -f $$tmp