[patch] Fix --with-babeltrace with gcc-4.9.1

Jan Kratochvil
2014-08-04T20:38:54Z

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Hi,

when I tried to use --with-babeltrace on Fedora Rawhide x86_64
using gcc-4.9.1-3.fc22.x86_64 I got:

checking for libbabeltrace... no
configure: error: babeltrace is missing or unusable
Makefile:7973: recipe for target 'configure-gdb' failed

configure:15890: checking for libbabeltrace
configure:15918: gcc -o conftest -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -Werror -static-libstdc++ -static-libgcc -Wl,-z,relro conftest.c -lselinux -lncurses -lz -lm -ldl /usr/lib64/libbabeltrace.so /usr/lib64/libbabeltrace-ctf.so >&5
conftest.c: In function 'main':
conftest.c:198:21: error: unused variable 'pos' [-Werror=unused-variable]
struct bt_iter_pos *pos = bt_iter_get_pos (bt_ctf_get_iter (NULL));
^
cc1: all warnings being treated as errors
configure:15918: $? = 1
configure: failed program was:

The patch below fixes it for me.

In configure.ac there is above this check:
# Append -Werror to CFLAGS so that configure can catch the warning
# "assignment from incompatible pointer type", which is related to
# the babeltrace change from 1.0.3 to 1.1.0. Babeltrace 1.1.0 works
# in GDB, while babeltrace 1.0.3 is broken.
# AC_LIB_HAVE_LINKFLAGS may modify CPPFLAGS in it, so it should be
# safe to save and restore CFLAGS here.
saved_CFLAGS=$CFLAGS
CFLAGS="$CFLAGS -Werror"

Maybe it would be easier to use there:
CFLAGS="$CFLAGS -Werror -Wno-unused-variable"

But maybe -Werror is cross-compiler compatible while -Wno-unused-variable is
not, I have no idea.

Jan

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gdb/
2014-08-04 Jan Kratochvil <jan.kratochvil@redhat.com>

* configure.ac (--with-babeltrace): Use 'pos'.
* configure: Regenerate.

diff --git a/gdb/configure.ac b/gdb/configure.ac
index 70d0964..07d2f00 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -2437,6 +2437,7 @@ else
struct bt_ctf_event *event = NULL;
const struct bt_definition *scope;

+ (void) pos; /* Prevent -Werror=unused-variable. */
scope = bt_ctf_get_top_level_scope (event,
BT_STREAM_EVENT_HEADER);
bt_ctf_get_uint64 (bt_ctf_get_field (event, scope, "id"));
diff --git a/gdb/configure b/gdb/configure
index 809326a..b983d16 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -15344,6 +15344,7 @@ struct bt_iter_pos *pos = bt_iter_get_pos (bt_ctf_get_iter (NULL));
struct bt_ctf_event *event = NULL;
const struct bt_definition *scope;

+ (void) pos; /* Prevent -Werror=unused-variable. */
scope = bt_ctf_get_top_level_scope (event,
BT_STREAM_EVENT_HEADER);
bt_ctf_get_uint64 (bt_ctf_get_field (event, scope, "id"));