generic-library/libbsd
1
0
Fork 0
mirror of https://gitlab.freedesktop.org/libbsd/libbsd.git synced 2025-01-06 00:31:14 +01:00
Code Issues Projects Releases Wiki Activity

test: nlist: make resilient against -Wl,--gc-sections

Browse Source 
With linker sections GC enabled, we get a test failure in `nlist.c`:
```
nlist: nlist.c:72: main: Assertion `rc == 0' failed.
```

This turns out to be because several sections used by the test can be discarded:
```
ld: removing unused section '.text.func_pub' in file 'nlist.o'
ld: removing unused section '.bss.data_pub_uninit' in file 'nlist.o'
ld: removing unused section '.data.data_pub_init' in file 'nlist.o'
```

Reproduced with `CFLAGS="-Og -fdata-sections -ffunction-sections"` and
`LDFLAGS="-Wl,-O1 -Wl,--as-needed -Wl,--gc-sections -Wl,-z,start-stop-gc"`.

Additionally, `LDFLAGS="... -Wl,--print-gc-sections"` can help with diagnosing
which sections get removed.

We already mark these symbols as `used`, but we need `retain` [0] for them
to survive linker GC too.

[0] https://releases.llvm.org/18.1.0/tools/lld/docs/ELF/start-stop-gc.html#annotate-c-identifier-name-sections

Closes: !29
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Guillem Jover <guillem@hadrons.org>
This commit is contained in:
Sam James 2024-03-13 23:34:55 +00:00 committed by Guillem Jover
parent 2a3d521318
commit b62f36f305
1 changed files with 15 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
test/nlist.c
View File

@ -33,17 +33,29 @@
#include <fcntl.h>
#include <nlist.h>
#if defined(__has_attribute)
#if __has_attribute(__retain__)
#define ATTRIBUTE_RETAIN __attribute__((__retain__))
#else
#define ATTRIBUTE_RETAIN
#endif
#endif
static int data_prv_init = 50;
extern int data_pub_init;
extern int data_pub_uninit[2048];
extern int *data_pub_ptr;
/* GCC's __has_attribute has odd behavior for retain: https://gcc.gnu.org/PR99587 */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wattributes"
int *data_pub_ptr = &data_prv_init;
int data_pub_init __attribute__((__used__)) = 10;
int data_pub_uninit[2048] __attribute__((__used__));
int data_pub_init ATTRIBUTE_RETAIN __attribute__((__used__)) = 10;
int data_pub_uninit[2048] ATTRIBUTE_RETAIN __attribute__((__used__));
extern int
func_pub(void) __attribute__((__used__)) ;
func_pub(void) ATTRIBUTE_RETAIN __attribute__((__used__));
#pragma GCC diagnostic pop
int
func_pub(void)