Here is an example libxl module gcc command:
gcc  -O1 -fno-omit-frame-pointer -m64 -g -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement -Wno-unused-but-set-variable -Wno-unused-local-typedefs   -D__XEN_TOOLS__ -MMD -MF .libxl.o.d -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -fno-optimize-sibling-calls  -Werror -Wno-format-zero-length -Wmissing-declarations -Wno-declaration-after-statement -Wformat-nonliteral -I. -fPIC -pthread -I/root/xen/tools/libxl/../../tools/libxc/include -I/root/xen/tools/libxl/../../tools/include -I/root/xen/tools/libxl/../../tools/libxc/include -I/root/xen/tools/libxl/../../tools/include -I/root/xen/tools/libxl/../../tools/xenstore/include -I/root/xen/tools/libxl/../../tools/include -I/root/xen/tools/libxl/../../tools/blktap2/control -I/root/xen/tools/libxl/../../tools/blktap2/include -I/root/xen/tools/libxl/../../tools/include  -Wshadow -include /root/xen/tools/libxl/../../tools/config.h  -c -o libxl.o libxl.c


I was unable to successfully make libvirt (more on that later), but here is an example libvirt module gcc command:
/bin/bash ../libtool  --tag=CC   --mode=compile gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I.. -I../gnulib/lib -I../gnulib/lib -I.. -I../include -I../include -I./util -DIN_LIBVIRT -Dabs_topbuilddir="\"/root/libvirt-1.2.12\""      -I/usr/include/libnl3   -I/usr/include/libnl3   -I/usr/include/libxml2   -W -Waddress -Waggressive-loop-optimizations -Wall -Warray-bounds -Wattributes -Wbad-function-cast -Wbuiltin-macro-redefined -Wcast-align -Wchar-subscripts -Wclobbered -Wcomment -Wcomments -Wcoverage-mismatch -Wcpp -Wdeprecated-declarations -Wdisabled-optimization -Wdiv-by-zero -Wdouble-promotion -Wempty-body -Wendif-labels -Wextra -Wformat-contains-nul -Wformat-extra-args -Wformat-security -Wformat-y2k -Wformat-zero-length -Wfree-nonheap-object -Wignored-qualifiers -Wimplicit -Wimplicit-function-declaration -Wimplicit-int -Winit-self -Winline -Wint-to-pointer-cast -Winvalid-memory-model -Winvalid-pch -Wjump-misses-init -Wlogical-op -Wmain -Wmaybe-uninitialized -Wmissing-braces -Wmissing-declarations -Wmissing-field-initializers -Wmissing-include-dirs -Wmissing-parameter-type -Wmissing-prototypes -Wmultichar -Wnarrowing -Wnested-externs -Wnonnull -Wold-style-declaration -Wold-style-definition -Woverflow -Woverride-init -Wpacked-bitfield-compat -Wparentheses -Wpointer-arith -Wpointer-sign -Wpointer-to-int-cast -Wpragmas -Wreturn-local-addr -Wreturn-type -Wsequence-point -Wshadow -Wsizeof-pointer-memaccess -Wstrict-aliasing -Wstrict-prototypes -Wsuggest-attribute=const -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wsuggest-attribute=pure -Wswitch -Wsync-nand -Wtrampolines -Wtrigraphs -Wtype-limits -Wuninitialized -Wunknown-pragmas -Wunused -Wunused-but-set-parameter -Wunused-but-set-variable -Wunused-function -Wunused-label -Wunused-local-typedefs -Wunused-parameter -Wunused-result -Wunused-value -Wunused-variable -Wvarargs -Wvariadic-macros -Wvector-operation-performance -Wvolatile-register-var -Wwrite-strings -Wnormalized=nfc -Wno-sign-compare -Wjump-misses-init -Wno-format-nonliteral -Wframe-larger-than=4096 -fexceptions -fasynchronous-unwind-tables -fipa-pure-const -Wno-suggest-attribute=pure -Wno-suggest-attribute=const -fstack-protector-all      -I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include       -I./conf -g -O2 -MT util/libvirt_util_la-viralloc.lo -MD -MP -MF util/.deps/libvirt_util_la-viralloc.Tpo -c -o util/libvirt_util_la-viralloc.lo `test -f 'util/viralloc.c' || echo './'`util/viralloc.c
libtool: compile:  gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I.. -I../gnulib/lib -I../gnulib/lib -I.. -I../include -I../include -I./util -DIN_LIBVIRT -Dabs_topbuilddir=\"/root/libvirt-1.2.12\" -I/usr/include/libnl3 -I/usr/include/libnl3 -I/usr/include/libxml2 -W -Waddress -Waggressive-loop-optimizations -Wall -Warray-bounds -Wattributes -Wbad-function-cast -Wbuiltin-macro-redefined -Wcast-align -Wchar-subscripts -Wclobbered -Wcomment -Wcomments -Wcoverage-mismatch -Wcpp -Wdeprecated-declarations -Wdisabled-optimization -Wdiv-by-zero -Wdouble-promotion -Wempty-body -Wendif-labels -Wextra -Wformat-contains-nul -Wformat-extra-args -Wformat-security -Wformat-y2k -Wformat-zero-length -Wfree-nonheap-object -Wignored-qualifiers -Wimplicit -Wimplicit-function-declaration -Wimplicit-int -Winit-self -Winline -Wint-to-pointer-cast -Winvalid-memory-model -Winvalid-pch -Wjump-misses-init -Wlogical-op -Wmain -Wmaybe-uninitialized -Wmissing-braces -Wmissing-declarations -Wmissing-field-initializers -Wmissing-include-dirs -Wmissing-parameter-type -Wmissing-prototypes -Wmultichar -Wnarrowing -Wnested-externs -Wnonnull -Wold-style-declaration -Wold-style-definition -Woverflow -Woverride-init -Wpacked-bitfield-compat -Wparentheses -Wpointer-arith -Wpointer-sign -Wpointer-to-int-cast -Wpragmas -Wreturn-local-addr -Wreturn-type -Wsequence-point -Wshadow -Wsizeof-pointer-memaccess -Wstrict-aliasing -Wstrict-prototypes -Wsuggest-attribute=const -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wsuggest-attribute=pure -Wswitch -Wsync-nand -Wtrampolines -Wtrigraphs -Wtype-limits -Wuninitialized -Wunknown-pragmas -Wunused -Wunused-but-set-parameter -Wunused-but-set-variable -Wunused-function -Wunused-label -Wunused-local-typedefs -Wunused-parameter -Wunused-result -Wunused-value -Wunused-variable -Wvarargs -Wvariadic-macros -Wvector-operation-performance -Wvolatile-register-var -Wwrite-strings -Wnormalized=nfc -Wno-sign-compare -Wjump-misses-init -Wno-format-nonliteral -Wframe-larger-than=4096 -fexceptions -fasynchronous-unwind-tables -fipa-pure-const -Wno-suggest-attribute=pure -Wno-suggest-attribute=const -fstack-protector-all -I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include -I./conf -g -O2 -MT util/libvirt_util_la-viralloc.lo -MD -MP -MF util/.deps/libvirt_util_la-viralloc.Tpo -c util/viralloc.c  -fPIC -DPIC -o util/.libs/libvirt_util_la-viralloc.o

What compile flag differences would explain my failure?

Regarding libvirt build failure:

* I successfully installed dependencies with "apt-get build-dep libvirt"

* ./configure passed

* I ran plain 'make' but there was too little verbosity in the output to see the gcc flags.  I let make run to completion though.  I did notice these logs, but it did not cause make to fail:
make[3]: Entering directory `/root/libvirt-1.2.12/docs'
  GEN      html/index.html
missing XHTML1 DTD

* I ran a make clean, followed by "make V=1" to get more verbosity (see above log).  However, now the "missing XHTML1 DTD" messages causes build failure:

make[3]: Entering directory `/root/libvirt-1.2.12/docs'
missing XHTML1 DTD
cat: 404.html.tmp: No such file or directory
make[3]: *** [404.html] Error 1
make[3]: Leaving directory `/root/libvirt-1.2.12/docs'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/root/libvirt-1.2.12/docs'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/root/libvirt-1.2.12'
make: *** [all] Error 2

I did a little research.  based on https://bugzilla.redhat.com/show_bug.cgi?format=multiple&id=1135685 and similar threads, I installed this:

apt-get install w3c-dtd-xhtml

Plain 'make' now errors this way:
make[3]: Entering directory `/root/libvirt-1.2.12/docs'
Validating 404.html
warning: failed to load external entity "404.html.tmp"
make[3]: *** [404.html] Error 1
make[3]: Leaving directory `/root/libvirt-1.2.12/docs'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/root/libvirt-1.2.12/docs'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/root/libvirt-1.2.12'
make: *** [all] Error 2

Based on some other threads I also tried these things:

* apt-get install libcurl4-gnutls-dev
* edited /etc/xml/catalog and added these lines to the bottom inside <catalog>:
<rewriteSystem systemIdStartString="http://www.w3.org/TR/xhtml1/DTD/" rewritePrefix="file:///usr/share/xml/xhtml/schema/dtd/1.0/"/>
<rewriteURI uriStartString="http://www.w3.org/TR/xhtml1/DTD/" rewritePrefix="file:///usr/share/xml/xhtml/schema/dtd/1.0/"/>

build still fails.

On Wed, Mar 4, 2015 at 10:27 AM, Wayne Mills <wmills.on.gm@gmail.com> wrote:
I'm have a lot of difficulty implementing the actions suggested so far by those who've chimed in about this issue.  I've resolved now to do the following:

* make clean and make world on xen source, and capture build logs
* look up libxl build logs and see what compiler flags were used
* repeat above for libvirt source and virt-manager source
* report back on the compiler flag differences I'm seeing, if any.

I think that's probably the best I can hope to accomplish without getting further lost in the weeds.  If I can do this then maybe it will inform further steps.

Wayne

On Wed, Mar 4, 2015 at 7:17 AM, Wayne Mills <wmills.on.gm@gmail.com> wrote:
Thanks Guido, unfortunately no luck:

root@<server>:~/debian# grep DEB_CONFIGURE_EXTRA_ARGS *
grep: apparmor: Is a directory
grep: patches: Is a directory
grep: source: Is a directory
root@<server>:~/debian#
root@<server>:~/debian#
root@<server>:~/debian#
root@<server>:~/debian# grep DEB_CONFIGURE_EXTRA_ARGS */*
root@<server>:~/debian#
root@<server>:~/debian#
root@<server>:~/debian# grep DEB_CONFIGURE_EXTRA_ARGS */*/*
grep: */*/*: No such file or directory
root@<server>:~/debian#


On Wed, Mar 4, 2015 at 3:01 AM, Guido Günther <agx@sigxcpu.org> wrote:
On Tue, Mar 03, 2015 at 02:31:27PM -0500, Wayne Mills wrote:
> I downloaded and untarred the deb package and grepped for 'configure', but
> none of the hits were configure commands.  Is there a better way to find it?

Assuming this is still based on the Debian package look for
DEB_CONFIGURE_EXTRA_ARGS in debian/rules.

Cheers,
 -- Guido