An example to illustrate the kind of checks done:
[acme@newtoy multi-cu]$ cat a.c
struct foo {
int a;
char b;
};
void a_foo_print(struct foo *f)
{
printf("f.a=%d\n", f->a);
}
[acme@newtoy multi-cu]$ cat main.c
struct foo {
int a;
char b;
char c;
};
extern void a_foo_print(struct foo *f);
int main(void)
{
struct foo f = { .a = 10, };
a_foo_print(&f);
return 0;
}
[acme@newtoy multi-cu]$ cc -g -c a.c -o a.o
[acme@newtoy multi-cu]$ cc -g -c main.c -o main.o
[acme@newtoy multi-cu]$ cc a.o main.o -o m
[acme@newtoy multi-cu]$ pahole m
class: foo
first: a.c
current: main.c
nr_members: 2 != 3
padding: 3 != 2
[acme@newtoy multi-cu]$
Gotcha? In the above case this inconsistency wouldn't cause problems, as the
'c' member doesn't makes the struct bigger, it uses the padding, but what if we
inverted the members 'a' and 'b'?
Upcoming csets will check if the type and order of the members are the same,
should help in some complex projects where people insist on using #ifdefs in
struct definitions.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Simplifying options processing by using just pair of cu and class iterators and
using the list we were building just for --total_structure_stats for all
options, this way we don't print multiple times structures that are defined in
more than one object file when processing a multi-object file.
With this in place all the options will check if a struct definition in one
object file somehow doesn't matches the same struct definition in some other
object file, more checks will be put in place in the upcoming csets.
And, to show that this besides simplifying reduces the code size, lets use
codiff:
[acme@newtoy pahole]$ codiff build/pahole.before build/pahole
/home/acme/pahole/pahole.c:
structures__add | -143
class__filter | +147
main | -263
3 functions changed, 147 bytes added, 406 bytes removed
[acme@newtoy pahole]$
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
We should check if we're in a new byte offset, i.e. the previous bitfield is
gone, now it works well when two bitfields are found one after the other, like
in struct sk_buff.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
For cases where the compiler doesn't emits the whole struct definition for
things like base classes that don't have any of its members acessed, just the
ones in its descendants.
Will be used to avoid emiting hole anottations, since we don't have the
size of these classes we can't say if its smaller than the space allocated
by the compiler.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
So that languages such as C++ can have its inheritance concepts
covered, example:
[acme@newtoy examples]$ pahole qsettings.o QSettingsPrivate
/* io/qsettings_p.h:159 */
class QSettingsPrivate {
class QObjectPrivate; /* ancestor class */ /* 0 0 */
/* XXX 56 bytes hole, try to pack */
/* --- cacheline 1 boundary (32 bytes) was 24 bytes ago --- */
class QStack<QSettingsGroup> groupStack; /* 56 4 */
class QString groupPrefix; /* 60 4 */
/* --- cacheline 2 boundary (64 bytes) --- */
int spec; /* 64 4 */
bool fallbacks; /* 68 1 */
bool pendingChanges; /* 69 1 */
/* XXX 2 bytes hole, try to pack */
enum Status status; /* 72 4 */
}; /* size: 76, cachelines: 3 */
/* sum members: 18, holes: 2, sum holes: 58 */
/* last cacheline: 12 bytes */
Nevermind about the "/* XXX 56 bytes hole, try to pack */" and sizeof(class
QObjectPrivate) being zero, its just gcc compressing the DWARF tags avoiding
including definitions that are not used in this specific object file, i.e.
there are not accesses to 'class QObjectPrivate' members.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
We want just DW_TAG_structure_type classes, but for now there are
enums, C++ inline classes, etc, have to fix this later.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
That is to find structs that have combinable holes, trying to pack the struct
by suggesting a move, for now it just prints structs that have holes that can
be combined, but these hints are not guaranteed to generate struct size
reductions, more has to be done and that involves understanding the alignment
rules that depend on the arch being 32 or 64 bits, but it at least reduces the
number of packing candidates.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This new function searches the first member before the one being traversed that
has a bit hole (or byte_hole, I've just normalised it on bits to make it
generic) that can be used to combine with the class_member at hand to possibly
kill a hole, possibly because for now it doesn't guarantees that moving the
member being traversed to just after the hole after the member returned by
class__find_bit_hole will indeed reduce the struct size, but its a good first
stab, next csets should provide a member to start from so that we can try to
find other holes after the one that proved not enough to reduce the struct
size.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
So that we can see only the structs that have more than the specified number of
bit holes.
Can be combined with --holes to see structs that have bit and byte holes.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Not printing the identation neither the newline, so that in the next csets
it'll be possible to show members that cross cacheline boundaries and also do
multiple levels of identation when we start supporting classes within classes
printing, to properly support C++.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Now we support classes within classes, i.e. DW_TAG_structure_type entries
within DW_TAG_structure_type, a C++ feature, see the FIXME in the new code.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
To fix this on parisc:
acme@parisc:~/pahole$ make
gcc -g -O2 -Wall -I. -I/usr/include/elfutils -c -o pahole.o pahole.c
gcc -g -O2 -Wall -I. -I/usr/include/elfutils -c -o classes.o classes.c
gcc -shared \
-o libclasses.so.1.0.0 classes.o
/usr/bin/ld: classes.o: relocation R_PARISC_DPREL21L can not be used when making a shared object; recompile with -fPIC
classes.o: could not read symbols: Bad value
collect2: ld returned 1 exit status
make: *** [libclasses.so] Error 1
acme@parisc:~/pahole$
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
These are currently only used by pahole and would live in classes otherwise.
Signed-off-by: Bernhard Fischer <rep.nop@aon.at>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
avoid mixing declarations and code to please ISO C90.
Signed-off-by: Bernhard Fischer <rep.nop@aon.at>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Build classes.c as a library. If STATIC=1, then link against the static lib,
else use a shared libclasses.
For the lazy, specify an rpath when linking dynamically (for now).
Set initial libclasses version to 1.0.0, don't use any fancy ld flags for now.
Signed-off-by: Bernhard Fischer <rep.nop@aon.at>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
The minimum number of holes that a struct must have for it to be
reported, to help in combining holes.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
pahole -D /pub/scm/linux/kernel/git/acme/net-2.6.20/include/net/ \
../OUTPUT/qemu/net-2.6.20/net/ipv4/tcp.o
Will exclude all the classes that were defined in files in the
/pub/scm/linux/kernel/git/acme/net-2.6.20/include/net/ directory, note that its
a prefix, not a directory, so one could as well pass
/pub/scm/linux/kernel/git/acme/net-2.6.20/include/net/tcp_ to exclude just the
files in the include/net directory and that start with 'tcp_'.
Now I think I implemented what Bernard wanted, and that is useful for me
as well, of course :-)
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
To simplify the callsites and make implementing the same thing on the other
dwarves (prefcnt, pfunct, etc) easy.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Doesn't make that much sense for structs, because of the usual includes hell in
most projects, but makes sense for pfunct, so implement it now and later move
it to classes.c.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
That checks for constraints, the first one being a exclude prefix, and is used
by all the iterators.
Additional constraints can be things like specifying prefixes for compilation
unit names, i.e. "show me only the object files which name starts with
net/ipv4/", etc.
Initial patch provided by Bernhard Fischer, who also had the --exclude idea.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Correct short option for nr_members in help text.
Signed-off-by: Bernhard Fischer <rep.nop@aon.at>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>