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tst_libext2fs: Avoid multiple definition of global variables

PATCH Superseded Lukas Czerner 4 participants 8 messages Jan 30, 2020 – Feb 28, 2020

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Lukas Czerner

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#0 lore raw

PATCH 1/1 tst_libext2fs: Avoid multiple definition of global variables

gcc version 10 changed the default from -fcommon to -fno-common and as a result e2fsprogs unit 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 creating an extern declaration of said variables in debugfs.h and just setting them in tst_libext2fs.c without additional declaration.

Signed-off-by Lukas Czerner <[email protected]>
---
 debugfs/debugfs.h          | 2 ++
 lib/ext2fs/tst_libext2fs.c | 5 +++--
 2 files changed, 5 insertions(+), 2 deletions(-)
debugfs/debugfs.h +2 -0
index 477d9bbb..956517bc 100644
@@ -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);
lib/ext2fs/tst_libext2fs.c +3 -2
index 3e7497cd..43f0d153 100644
@@ -28,9 +28,7 @@
  * Hook in new commands into debugfs
  * Override debugfs's prompt
  */
-const char *debug_prog_name = "tst_libext2fs";
 extern ss_request_table libext2fs_cmds;
-ss_request_table *extra_cmds = &libext2fs_cmds;
 
 static int print_blocks_proc(ext2_filsys fs EXT2FS_ATTR((unused)),
 			     blk64_t *blocknr, e2_blkcnt_t blockcnt,

@@ -51,6 +49,9 @@ void do_block_iterate(int argc, char **argv, int sci_idx EXT2FS_ATTR((unused)),
 	int		err = 0;
 	int		flags = 0;
 
+	debug_prog_name = "tst_libext2fs";
+	extra_cmds = &libext2fs_cmds;
+
 	if (common_args_process(argc, argv, 2, 3, argv[0], usage, 0))
 		return;
Signature · 1 line
2.21.1
Reviewed-by on v1 1/1
#1 lore raw
Quoted 10 lines · Lukas Czerner

gcc version 10 changed the default from -fcommon to -fno-common and as a result e2fsprogs unit 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.

Quoted 5 lines

Fix the problem by creating an extern declaration of said variables in debugfs.h and just setting them in tst_libext2fs.c without additional declaration.

Signed-off-by Lukas Czerner <[email protected]>

This looks fine to me.

Reviewed-by Eric Sandeen <[email protected]>

Is there any need to fix the one in lib/ext2fs/extent.c ? It's only there under #ifdef DEBUG though.

Thanks,
-Eric

author
#2 lore raw
Quoted 15 lines · Eric Sandeen
Quoted 14 lines · Lukas Czerner

gcc version 10 changed the default from -fcommon to -fno-common and as a result e2fsprogs unit 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 creating an extern declaration of said variables in debugfs.h and just setting them in tst_libext2fs.c without additional declaration.

Quoted 8 lines
Quoted 1 line
Signed-off-by Lukas Czerner <[email protected]>

This looks fine to me.

Reviewed-by Eric Sandeen <[email protected]>

Is there any need to fix the one in lib/ext2fs/extent.c ? It's only there under #ifdef DEBUG though.

Yeah, but if we ever want to use DEBUG macro it would fail with -fno-common. Uff, I guess I have to fix this one as well.

Thanks Eric,
-Lukas

Quoted 4 lines

Thanks,
-Eric

author
#3 lore raw

PATCH v2 1/1 tst_libext2fs: Avoid multiple definition of global variables

In reply to Lukas Czerner

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 <[email protected]>

---
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(-)
debugfs/debugfs.c +6 -0
index 9b701455..5e8f8bdd 100644
@@ -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;
debugfs/debugfs.h +2 -0
index 477d9bbb..956517bc 100644
@@ -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);
lib/ext2fs/Makefile.in +1 -1
index c2163bf5..f754b952 100644
@@ -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 $<"
Signature · 1 line
2.21.1
#4 lore raw
Quoted 16 lines · Lukas Czerner

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.

Quoted 3 lines
Signed-off-by Lukas Czerner <[email protected]>

---
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

#5 lore raw
Quoted 21 lines · Eric Sandeen
Quoted 16 lines · Lukas Czerner

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.

Quoted 3 lines
Signed-off-by Lukas Czerner <[email protected]>

---
v2: Previous fix wasn't really working properly

Quoted 5 lines

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

Reviewed-by on v2 1/1
#6 lore raw
In reply to Lukas Czerner
Quoted 16 lines · Lukas Czerner

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.

Quoted 3 lines
Signed-off-by Lukas Czerner <[email protected]>

---
v2: Previous fix wasn't really working properly

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

Reviewed-by Eric Sandeen <[email protected]>
Applied
#7 lore raw
In reply to Lukas Czerner
Quoted 10 lines · Lukas Czerner

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.

Quoted 7 lines

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 <[email protected]>

Applied, thanks.

- Ted