Public bug reported:
The default use of --as-needed with ld in oneiric breaks some implicit
rules used by make. These rules invoke cc with command line in which
$(LDFLAGS) appears before the source file being compiled or object file
being linked, and that order is preserved when cc invokes ld. As a
result, ld thinks the libraries listed in LDFLAGS aren't needed and
doesn't link them.
For example, consider a C source file, example.c:
#include "zlib.h"
int main() {
inflateInit(0);
}
and a Makefile:
LDFLAGS = -lz
example: example.o
Running make invokes make's implicit rule for linking a single object
file ("$(CC) $(LDFLAGS) n.o $(LOADLIBES) $(LDLIBS)"), and produces the
following output:
cc -c -o example.o example.c
cc -lz example.o -o example
/tmp/ccovHoBb.o: In function `main':
example.c:(.text+0x14): undefined reference to `inflateInit_'
collect2: ld returned 1 exit status
make: *** [example] Error 1
Behind the scenes, ld is being run as "ld --as-needed ... -lz example.o
...". When ld processes libz, it doesn't know about any of the
references from example.o, so it doesn't include it.
This problem seems to have prevented at least one package (sawfish-
pager) from being included in oneiric because it would no longer
compile, and I worry that there may be others.
I'm not sure what the best solution would be. One possibility would be
patching make to change its implicit rules, but that could have serious
consequences elsewhere. At the very least, it would necessitate patching
other programs that run UNIX makefiles, such as remake and pmake.
** Affects: ubuntu
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/874588
Title:
ld --as-needed breaks implicit rules in make
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