Experimental Physics and
Industrial Control System

I'm attempting to build EPICS base for a VMIVME7805 intel based VME card.  The kernel I

have is 3.16.7.  We are using Buildroot on an SL7.5 host machine.  I'm attempting to build
3.14.12.8.

I had found Bruno Martins'  wiki page: https://wiki-ext.aps.anl.gov/epics/index.php/How_To_cross_compile_EPICS_and_a_IOC_to_an_old_x86_Linux_system
which is very helpful.  However, Buildroot segregates the build tools from the lib & bin & include
files.

From Buildroot, my build tools are in:

.../host/usr/bin/i686-buildroot-linux-uclibc/
And, my staged lib & include & bin files are in:
.../host/staging/.

So, here's what I have in ./base/configure/os/CONFIG_SITE.Common.linux-686:
# Location of the cross-compile toolchain
VMIVME=/usr/local/products/elsd/vmivme7805/linux-3.16.7_generic/output
GNU_DIR=$(VMIVME)/host/usr
GNU_TARGET=i686-buildroot-linux-uclibc

SHRLIB_DEPLIB_DIRS += $(VMIVME)/staging/usr/lib
PROD_DEPLIB_DIRS   += $(VMIVME)/staging/usr/lib

In order to get the headers correct, I also modified ./base/configure/CONFIG.CrossCommon:
#GNU_TARGET_INCLUDE_DIR = $(wildcard $(GNU_TARGET:%=$(GNU_DIR)/%/include))
#GNU_TARGET_LIB_DIR = $(wildcard $(GNU_TARGET:%=$(GNU_DIR)/%/lib))
GNU_TARGET_INCLUDE_DIR = $(VMIVME)/staging/usr/include
GNU_TARGET_LIB_DIR     = $(VMIVME)/staging/usr/lib

It appears that I can compile everything; for example (the last compile command):
/usr/local/products/elsd/vmivme7805/linux-3.16.7_generic/output/host/usr/bin/i686-buildroot-linux-uclibc-g++ -o libCom.so.3.14 -shared -fPIC -L/usr/local/products/elsd/vmivme7805/linux-3.16.7_generic/output/staging/usr/lib -Wl,-rpath,/usr/local/products/elsd/vmivme7805/linux-3.16.7_generic/output/staging/usr/lib        -m32    -L/usr/local/products/elsd/vmivme7805/linux-3.16.7_generic/output/host/usr/../../staging/usr/lib            bucketLib.o epicsRingPointer.o epicsRingBytes.o postfix.o calcPerform.o cvtFast.o resourceLib.o epicsOnce.o epicsSingletonMutex.o dbmf.o ellLib.o envSubr.o envData.o errlog.o errSymLib.o errSymTbl.o fdmgr.o fdManager.o freeListLib.o gpHashLib.o iocsh.o registry.o libComRegister.o iocLog.o logClient.o macCore.o macEnv.o macUtil.o aToIPAddr.o adjustment.o cantProceed.o epicsConvert.o epicsExit.o epicsStdlib.o epicsString.o truncateFile.o ipAddrToAsciiAsynchronous.o epicsUnitTest.o epicsThread.o epicsMutex.o epicsEvent.o epicsTime.o epicsMessageQueue.o epicsMath.o epicsGeneralTime.o osiClockTime.o osdSock.o osdSockAddrReuse.o osiSock.o systemCallIntMech.o epicsSocketConvertErrnoToString.o osdAssert.o osdFindSymbol.o osdInterrupt.o osdPoolStatus.o osdSignal.o osdEnv.o epicsReadline.o epicsTempFile.o epicsStdio.o osdStdio.o osdThread.o osdMutex.o osdEvent.o osdTime.o osdProcess.o osdNetIntf.o osdMessageQueue.o devLibVME.o devLibVMEOSD.o taskwd.o epicsTimer.o timer.o timerQueue.o timerQueueActive.o timerQueueActiveMgr.o timerQueuePassive.o tsDefs.o      -lpthread   -lreadline -lncurses -lm -lrt -ldl -lgcc

But when it comes to loading shared libraries, it fails (next command in make):
/scratch/products/elsd/vmivme7805/linux-3.16.7_generic/output/host/usr/bin/../lib/gcc/i686-buildroot-linux-uclibc/4.8.3/../../../../i686-buildroot-linux-uclibc/bin/ld: cannot find /lib/libubacktrace.so.0
collect2: error: ld returned 1 exit status
make[3]: *** [libCom.so.3.14] Error 1

Firstly, I didn't understand why libubacktrace.so (used by uclibc) appears to have a hard-coded path.

However, when I created a softlink (yes, a cheat) so that it was found, the build failed next on readline;
which tells me, if I understand it, that SHRLIB_DEPLIB_DIRS += $(VMIVME)/staging/usr/lib didn't work
as expected.  From Andrew's response to the 2013 query, the problem appears to be more
subtle; i.e. don't build a linux-x86 system on a linux-x86 system since it will always build for the host first.

I would greatly appreciate a better understanding of the problem and how to implement a remedy?
The application developer's guide does not appear (perhaps I'm missing something) to deal with
the situation presented by Buildroot's segregating build tools from target libraries, header files, etc.

-- 
Complexity comes for free, Simplicity you have to work for.