https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122516
Bug ID: 122516
Summary: [avr] 'retain' attribute ignored even though
HAVE_GAS_SHF_GNU_RETAIN
Product: gcc
Version: 15.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: gjl at gcc dot gnu.org
Target Milestone: ---
int main (void) { return 0; }
__attribute__((used,retain,section(".text.func")))
void func (void) { }
$ avr-gcc-15 retain.c -S -Os && cat retain.s
retain.c:4:1: warning: 'retain' attribute ignored [-Wattributes]
4 | void func (void) { }
| ^~~~
The generated assembly is:
.section .text.func,"ax",@progbits
.global func
.type func, @function
func:
ret
and hence func() is discarded with -Wl,--gc-sections. Expected assembly:
.section .text.func,"axR",@progbits
so that the function is retained by the linker. When I add the "R" flag by
hand, then -Wl,--gc-sections doesn't kill func() any more.
Notice that auto-host.h reads:
$ grep -n SHF_GNU *.h
auto-host.h:1565:/* Define 0/1 if your assembler supports marking sections with
SHF_GNU_RETAIN
auto-host.h:1568:#define HAVE_GAS_SHF_GNU_RETAIN 1
So the R flag is supported, but defaults.h has:
/* This determines whether or not we support marking sections with
SHF_GNU_RETAIN flag. Also require .init_array/.fini_array section
for constructors and destructors. */
#ifndef SUPPORTS_SHF_GNU_RETAIN
#if HAVE_GAS_SHF_GNU_RETAIN && HAVE_INITFINI_ARRAY_SUPPORT
#define SUPPORTS_SHF_GNU_RETAIN 1
#else
#define SUPPORTS_SHF_GNU_RETAIN 0
#endif
#endif
I don't quite understand why HAVE_INITFINI_ARRAY_SUPPORT is required to retain
functions. It's perfectly fine to retain functions for avr and maybe on many
other targets, too.
Configured with: ../../source/gcc-master/configure --target=avr --disable-nls
--with-dwarf2 --with-gnu-as --with-gnu-ld --with-long-double=64
--disable-libcc1 --disable-shared --enable-languages=c,c++
