Add a compilation flag that adds unwind info to all files that are present in the stack starting from MPI_Init.

This is so when a debugger attaches using MPIR, it can step out of this stack back into main.
This cannot be done with certain aggressive optimisations and missing debug information.

Signed-off-by: James Clark <james.clark@arm.com>
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>

Co-authored-by: Jeff Squyres <jsquyres@cisco.com>

Author: James-A-Clark

config/orte_setup_debugger_flags.m4

@@ -10,7 +10,7 @@ dnl Copyright (c) 2004-2007 High Performance Computing Center Stuttgart,
 dnl                         University of Stuttgart.  All rights reserved.
 dnl Copyright (c) 2004-2005 The Regents of the University of California.
 dnl                         All rights reserved.
-dnl Copyright (c) 2006-2009 Cisco Systems, Inc.  All rights reserved.
+dnl Copyright (c) 2006-2019 Cisco Systems, Inc.  All rights reserved.
 dnl Copyright (c) 2006-2009 Sun Microsystems, Inc.  All rights reserved.
 dnl Copyright (c) 2006-2007 Los Alamos National Security, LLC.  All rights
 dnl                         reserved.
@@ -24,6 +24,28 @@ dnl
 dnl $HEADER$
 dnl
 
+dnl Check to see if specific CFLAGS work
+dnl $1: compiler flags to check
+dnl $2: Action if the flags work
+dnl $3: Action if the flags do not work
+AC_DEFUN([_ORTE_SETUP_DEBUGGER_FLAGS_TRY_CFLAGS],[
+    OPAL_VAR_SCOPE_PUSH([ORTE_SETUP_DEBUGGER_FLAGS_CFLAGS_save])
+
+    ORTE_SETUP_DEBUGGER_FLAGS_CFLAGS_save=$CFLAGS
+    AC_MSG_CHECKING([if $1 compiler flag works])
+    CFLAGS="$CFLAGS $1"
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[int i = 3;])],
+        [ORTE_SETUP_DEBUGGER_FLAGS_HAPPY=yes],
+        [ORTE_SETUP_DEBUGGER_FLAGS_HAPPY=no])
+    AC_MSG_RESULT([$ORTE_SETUP_DEBUGGER_FLAGS_HAPPY])
+    CFLAGS=$ORTE_SETUP_DEBUGGER_FLAGS_CFLAGS_save
+
+    OPAL_VAR_SCOPE_POP
+
+    AS_IF([test $ORTE_SETUP_DEBUGGER_FLAGS_HAPPY = yes],
+          [$2], [$3])
+])
+
 AC_DEFUN([ORTE_SETUP_DEBUGGER_FLAGS],[
     #
     # Do a final process of the CFLAGS to make a WITHOUT_OPTFLAGS
@@ -53,4 +75,22 @@ AC_DEFUN([ORTE_SETUP_DEBUGGER_FLAGS],[
 
     AC_SUBST(CFLAGS_WITHOUT_OPTFLAGS)
     AC_SUBST(DEBUGGER_CFLAGS)
+
+    # Check for compiler specific flag to add in unwind information.
+    # This is needed when attaching using MPIR to unwind back to the
+    # user's main function. Certain optimisations can prevent GDB from
+    # producing a stack when explicit unwind information is unavailable.
+    # This is implied by -g, but we want to save space and don't need
+    # full debug symbols.
+    _ORTE_SETUP_DEBUGGER_FLAGS_TRY_CFLAGS([-fasynchronous-unwind-tables],
+        [MPIR_UNWIND_CFLAGS="-fasynchronous-unwind-tables"],
+        [_ORTE_SETUP_DEBUGGER_FLAGS_TRY_CFLAGS([-Meh_frame -Mframe],
+            [MPIR_UNWIND_CFLAGS="-Meh_frame -Mframe"],
+            [MPIR_UNWIND_CFLAGS=-g])
+        ])
+
+    AC_MSG_CHECKING([for final compiler unwind flags])
+    AC_MSG_RESULT([$MPIR_UNWIND_CFLAGS])
+
+    AC_SUBST(MPIR_UNWIND_CFLAGS)
 ])

ompi/runtime/Makefile.am

@@ -33,10 +33,19 @@ headers += \
 lib@OMPI_LIBMPI_NAME@_la_SOURCES += \
         runtime/ompi_mpi_abort.c \
         runtime/ompi_mpi_dynamics.c \
-        runtime/ompi_mpi_init.c \
         runtime/ompi_mpi_finalize.c \
         runtime/ompi_mpi_params.c \
         runtime/ompi_mpi_preconnect.c \
 	runtime/ompi_cr.c \
 	runtime/ompi_info_support.c \
 	runtime/ompi_spc.c
+
+# The MPIR portion of the library must be built with flags to
+# enable stepping out of MPI_INIT into main.
+# Use an intermediate library to isolate the debug object.
+noinst_LTLIBRARIES += libompi_mpir.la
+libompi_mpir_la_SOURCES = \
+	runtime/ompi_mpi_init.c
+libompi_mpir_la_CFLAGS = $(MPIR_UNWIND_CFLAGS)
+
+lib@OMPI_LIBMPI_NAME@_la_LIBADD += libompi_mpir.la

orte/mca/ess/Makefile.am

@@ -19,6 +19,10 @@
 
 AM_CPPFLAGS = $(LTDLINCL)
 
+# Add unwind flags because files in this tree are
+# involved in startup.
+AM_CFLAGS = $(MPIR_UNWIND_CFLAGS)
+
 # main library setup
 noinst_LTLIBRARIES = libmca_ess.la
 libmca_ess_la_SOURCES =

orte/mca/ess/pmi/Makefile.am

@@ -11,6 +11,12 @@
 # $HEADER$
 #
 
+# Add MPIR unwind flags because files in this tree are
+# involved in startup. This is not needed in the other
+# subdirs in orte/mca/ess because the other components are
+# solely used by daemons and thus are not accessible by the debugger.
+AM_CFLAGS = $(MPIR_UNWIND_CFLAGS)
+
 AM_CPPFLAGS = $(ess_pmi_CPPFLAGS)
 
 sources = \

orte/runtime/Makefile.am

@@ -38,7 +38,6 @@ headers += \
 
 lib@ORTE_LIB_PREFIX@open_rte_la_SOURCES += \
         runtime/orte_finalize.c \
-        runtime/orte_init.c \
         runtime/orte_locks.c \
         runtime/orte_globals.c \
         runtime/orte_quit.c \
@@ -52,3 +51,12 @@ lib@ORTE_LIB_PREFIX@open_rte_la_SOURCES += \
         runtime/orte_cr.c \
         runtime/orte_data_server.c \
         runtime/orte_info_support.c
+
+# The MPIR portion of the library must be built with flags to
+# enable stepping out of MPI_INIT into main.
+# Use an intermediate library to isolate the debug object.
+noinst_LTLIBRARIES += libruntime_mpir.la
+libruntime_mpir_la_SOURCES = \
+        runtime/orte_init.c
+libruntime_mpir_la_CFLAGS = $(MPIR_UNWIND_CFLAGS)
+lib@ORTE_LIB_PREFIX@open_rte_la_LIBADD += libruntime_mpir.la