[v2] tst_libext2fs: Avoid multiple definition of global variables
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Message ID 20200210152459.19903-1-lczerner@redhat.com
State New
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  • [v2] tst_libext2fs: Avoid multiple definition of global variables
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Commit Message

Lukas Czerner Feb. 10, 2020, 3:24 p.m. UTC
gcc version 10 changed the default from -fcommon to -fno-common and as a
result e2fsprogs make check tests fail because tst_libext2fs.c end up
with a build error.

This is because it defines two global variables debug_prog_name and
extra_cmds that are already defined in debugfs/debugfs.c. With -fcommon
linker was able to resolve those into the same object, however with
-fno-common it's no longer able to do it and we end up with multiple
definition errors.

Fix the problem by using SKIP_GLOBDEFS macro to skip the variables
definition in debugfs.c. Note that debug_prog_name is also defined in
lib/ext2fs/extent.c when DEBUG macro is used, but this does not work even
with older gcc versions and is never used regardless so I am not going to
bother with it.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
v2: Previous fix wasn't really working properly

 debugfs/debugfs.c      | 6 ++++++
 debugfs/debugfs.h      | 2 ++
 lib/ext2fs/Makefile.in | 2 +-
 3 files changed, 9 insertions(+), 1 deletion(-)

Comments

Eric Sandeen Feb. 11, 2020, 8:22 p.m. UTC | #1
On 2/10/20 9:24 AM, Lukas Czerner wrote:
> gcc version 10 changed the default from -fcommon to -fno-common and as a
> result e2fsprogs make check tests fail because tst_libext2fs.c end up
> with a build error.
> 
> This is because it defines two global variables debug_prog_name and
> extra_cmds that are already defined in debugfs/debugfs.c. With -fcommon
> linker was able to resolve those into the same object, however with
> -fno-common it's no longer able to do it and we end up with multiple
> definition errors.
> 
> Fix the problem by using SKIP_GLOBDEFS macro to skip the variables
> definition in debugfs.c. Note that debug_prog_name is also defined in
> lib/ext2fs/extent.c when DEBUG macro is used, but this does not work even
> with older gcc versions and is never used regardless so I am not going to
> bother with it.
> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> ---
> v2: Previous fix wasn't really working properly

What was not working properly?

It seemed reasonable to me.  The new mechanism looks like it would work,
but the first patch seemed more obvious, so I'd like to know what the problem
was.

Thanks,
-Eric
Eric Sandeen Feb. 11, 2020, 9:08 p.m. UTC | #2
On 2/11/20 2:22 PM, Eric Sandeen wrote:
> On 2/10/20 9:24 AM, Lukas Czerner wrote:
>> gcc version 10 changed the default from -fcommon to -fno-common and as a
>> result e2fsprogs make check tests fail because tst_libext2fs.c end up
>> with a build error.
>>
>> This is because it defines two global variables debug_prog_name and
>> extra_cmds that are already defined in debugfs/debugfs.c. With -fcommon
>> linker was able to resolve those into the same object, however with
>> -fno-common it's no longer able to do it and we end up with multiple
>> definition errors.
>>
>> Fix the problem by using SKIP_GLOBDEFS macro to skip the variables
>> definition in debugfs.c. Note that debug_prog_name is also defined in
>> lib/ext2fs/extent.c when DEBUG macro is used, but this does not work even
>> with older gcc versions and is never used regardless so I am not going to
>> bother with it.
>>
>> Signed-off-by: Lukas Czerner <lczerner@redhat.com>
>> ---
>> v2: Previous fix wasn't really working properly
> 
> What was not working properly?
> 
> It seemed reasonable to me.  The new mechanism looks like it would work,
> but the first patch seemed more obvious, so I'd like to know what the problem
> was.

I built e2fsprogs & ran make check from git on Fedora Rawhide w/ your first patch,
and it all seemed to work fine so I'll just stand by for more info.  :)

-Eric
Eric Sandeen Feb. 13, 2020, 11:08 p.m. UTC | #3
On 2/10/20 9:24 AM, Lukas Czerner wrote:
> gcc version 10 changed the default from -fcommon to -fno-common and as a
> result e2fsprogs make check tests fail because tst_libext2fs.c end up
> with a build error.
> 
> This is because it defines two global variables debug_prog_name and
> extra_cmds that are already defined in debugfs/debugfs.c. With -fcommon
> linker was able to resolve those into the same object, however with
> -fno-common it's no longer able to do it and we end up with multiple
> definition errors.
> 
> Fix the problem by using SKIP_GLOBDEFS macro to skip the variables
> definition in debugfs.c. Note that debug_prog_name is also defined in
> lib/ext2fs/extent.c when DEBUG macro is used, but this does not work even
> with older gcc versions and is never used regardless so I am not going to
> bother with it.
> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> ---
> v2: Previous fix wasn't really working properly


Lukas explained the problem to me - wow the test binaries are tricky.  ;)

Reviewed-by: Eric Sandeen <sandeen@redhat.com>

Patch
diff mbox series

diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
index 9b701455..5e8f8bdd 100644
--- a/debugfs/debugfs.c
+++ b/debugfs/debugfs.c
@@ -48,8 +48,14 @@  extern char *optarg;
 int journal_enable_debug = -1;
 #endif
 
+/*
+ * There must be only one definition if we're hooking in extra commands or
+ * chaging default prompt. Use -DSKIP_GLOBDEF for that.
+ */
+#ifndef SKIP_GLOBDEFS
 ss_request_table *extra_cmds;
 const char *debug_prog_name;
+#endif
 int ss_sci_idx;
 
 ext2_filsys	current_fs;
diff --git a/debugfs/debugfs.h b/debugfs/debugfs.h
index 477d9bbb..956517bc 100644
--- a/debugfs/debugfs.h
+++ b/debugfs/debugfs.h
@@ -123,6 +123,8 @@  extern void do_set_block_group_descriptor(int argc, char **, int sci_idx, void *
 extern void do_dump_unused(int argc, char **argv, int sci_idx, void *infop);
 
 /* debugfs.c */
+extern ss_request_table *extra_cmds;
+extern const char *debug_prog_name;
 extern void internal_dump_inode(FILE *, const char *, ext2_ino_t,
 				struct ext2_inode *, int);
 
diff --git a/lib/ext2fs/Makefile.in b/lib/ext2fs/Makefile.in
index c2163bf5..f754b952 100644
--- a/lib/ext2fs/Makefile.in
+++ b/lib/ext2fs/Makefile.in
@@ -377,7 +377,7 @@  extent_cmds.c extent_cmds.h: $(top_srcdir)/debugfs/extent_cmds.ct
 
 debugfs.o: $(top_srcdir)/debugfs/debugfs.c
 	$(E) "	CC $<"
-	$(Q) $(CC) $(DEBUGFS_CFLAGS) -c $< -o $@
+	$(Q) $(CC) $(DEBUGFS_CFLAGS) -DSKIP_GLOBDEFS -c $< -o $@
 
 extent_inode.o: $(top_srcdir)/debugfs/extent_inode.c
 	$(E) "	CC $<"