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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>
103 lines
3.3 KiB
C
103 lines
3.3 KiB
C
/*
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* Copyright © 2017 Guillem Jover <guillem@hadrons.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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* THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <assert.h>
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#include <fcntl.h>
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#include <nlist.h>
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#if defined(__has_attribute)
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#if __has_attribute(__retain__)
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#define ATTRIBUTE_RETAIN __attribute__((__retain__))
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#else
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#define ATTRIBUTE_RETAIN
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#endif
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#endif
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static int data_prv_init = 50;
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extern int data_pub_init;
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extern int data_pub_uninit[2048];
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extern int *data_pub_ptr;
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/* GCC's __has_attribute has odd behavior for retain: https://gcc.gnu.org/PR99587 */
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wattributes"
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int *data_pub_ptr = &data_prv_init;
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int data_pub_init ATTRIBUTE_RETAIN __attribute__((__used__)) = 10;
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int data_pub_uninit[2048] ATTRIBUTE_RETAIN __attribute__((__used__));
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extern int
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func_pub(void) ATTRIBUTE_RETAIN __attribute__((__used__));
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#pragma GCC diagnostic pop
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int
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func_pub(void)
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{
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return 42;
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}
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int
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main(int argc, char **argv)
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{
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struct nlist nl[] = {
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{ .n_un.n_name = (char *)"main" },
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{ .n_un.n_name = (char *)"func_pub" },
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{ .n_un.n_name = (char *)"data_pub_uninit" },
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{ .n_un.n_name = (char *)"data_pub_init" },
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{ .n_un.n_name = (char *)"data_prv_init" },
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{ .n_un.n_name = NULL },
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};
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int rc;
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assert(*data_pub_ptr == 50);
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assert(nl[0].n_name == nl[0].n_un.n_name);
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rc = nlist(argv[0], nl);
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assert(rc == 0);
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#if defined(__powerpc64__) && _CALL_ELF == 1
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/* On PowerPC 64-bit ELFv1, the functions are stored in
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* the .text sections but they are accessed through a function
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* descriptor stored in a data section, for example for PowerPC
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* 64-bit that section is called .opd. */
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assert(nl[0].n_type == (N_DATA | N_EXT));
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assert(nl[1].n_type == (N_DATA | N_EXT));
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#else
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assert(nl[0].n_type == (N_TEXT | N_EXT));
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assert(nl[1].n_type == (N_TEXT | N_EXT));
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#endif
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assert(nl[2].n_type == (N_BSS | N_EXT));
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assert(nl[3].n_type == (N_DATA | N_EXT));
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assert(nl[4].n_type == (N_DATA));
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return 0;
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}
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