https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62287
Bug ID: 62287
Summary: gcc generates near call for extern weak function
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: breiten at lexmark dot com
The following code, from a linux driver, attempts to call a weak function, if
the address of that function is non-zero (i.e. defined in an earlier-loaded
module).
However, when configured for arm-eabi, a normal "bl" instruction is issued.
While it generates the logic to test and avoid the call if bar is NULL, we get
a relocation error when the driver is loaded, because 0 is too far away from
0xbf7xxxx. Verified this on 4.7.2, 4,8.3, and 4.9.0. gcc-4.2 generates the bx
opcode that I expect.
The current documentation for -mlong-calls" under "ARM options" states:
The exceptions to this rule are that weak function definitions, functions with
the ‘long-call’ attribute or the ‘section’ attribute, and functions that are
within the scope of a ‘ #pragma long_calls’ directive are always turned into
long calls.
I did see PR51643, which addresses this sort of problem for tail calls, and I
see it behave correctly if I modify the code below to allow a tail-call.
extern void bar(void)__attribute__((weak));
int foo()
{
if( bar)
bar();
return 0;
}
Here's my configuration/version info:
Target: arm-poky-linux-gnueabi
Configured with:
/bonus/scratch/gcc49/poky/gg-debug/tmp/work-shared/gcc-4.9.0-r0/gcc-4.9.0/configure
--build=x86_64-linux --host=x86_64-linux --target=arm-poky-linux-gnueabi
--prefix=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr
--exec_prefix=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr
--bindir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/bin/cortexa53-vfp-neon-poky-linux-gnueabi
--sbindir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/bin/cortexa53-vfp-neon-poky-linux-gnueabi
--libexecdir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/libexec/cortexa53-vfp-neon-poky-linux-gnueabi
--datadir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/share
--sysconfdir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/etc
--sharedstatedir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/com
--localstatedir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/var
--libdir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/lib/cortexa53-vfp-neon-poky-linux-gnueabi
--includedir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/include
--oldincludedir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/include
--infodir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/share/info
--mandir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/share/man
--disable-silent-rules --disable-dependency-tracking
--with-libtool-sysroot=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux
--enable-clocale=generic --with-gnu-ld --enable-shared --enable-languages=c,c++
--enable-threads=posix --disable-multilib --enable-c99 --enable-long-long
--enable-symvers=gnu --enable-libstdcxx-pch
--program-prefix=arm-poky-linux-gnueabi- --without-local-prefix
--enable-target-optspace --enable-lto --enable-libssp --disable-bootstrap
--disable-libmudflap --with-system-zlib --with-linker-hash-style=gnu
--enable-linker-build-id --with-ppl=no --with-cloog=no
--enable-checking=release --enable-cheaders=c_global
--with-gxx-include-dir=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/gg/usr/include/c++
--with-sysroot=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/gg
--with-build-sysroot=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/gg
--enable-poison-system-directories --disable-libunwind-exceptions
--with-mpfr=/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr
--with-system-zlib --disable-nls
Thread model: posix
gcc version 4.9.0 (GCC)
/bonus/scratch/gcc49/poky/gg-debug/tmp/sysroots/x86_64-linux/usr/bin/cortexa53-vfp-neon-poky-linux-gnueabi/arm-poky-linux-gnueabi-gcc
-Os -mabi=aapcs-linux -mcpu=cortex-a53 -S -o - p.c
.cpu cortex-a53
.fpu softvfp
.eabi_attribute 20, 1
.eabi_attribute 21, 1
.eabi_attribute 23, 3
.eabi_attribute 24, 1
.eabi_attribute 25, 1
.eabi_attribute 26, 2
.eabi_attribute 30, 4
.eabi_attribute 34, 1
.eabi_attribute 18, 4
.file "p.c"
.text
.align 2
.global foo
.type foo, %function
foo:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
stmfd sp!, {r3, lr}
ldr r3, .L8
cmp r3, #0
beq .L2
bl bar
.L2:
mov r0, #0
ldmfd sp!, {r3, pc}
.L9:
.align 2
.L8:
.word bar
.size foo, .-foo
.weak bar
.ident "GCC: (GNU) 4.9.0"
.section .note.GNU-stack,"",%progbits
