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Date:      Mon, 04 Jun 2018 21:02:48 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 228753] [i386] lld emits malformed DWARF info for crt1.o
Message-ID:  <bug-228753-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D228753

            Bug ID: 228753
           Summary: [i386] lld emits malformed DWARF info for crt1.o
           Product: Base System
           Version: CURRENT
          Hardware: i386
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: bin
          Assignee: bugs@FreeBSD.org
          Reporter: markj@FreeBSD.org

With an lld-linked i386 world, ld.bfd hangs when linking the following prog=
ram:

$ cat conftest.c
int k; int foo () { __builtin_alloca (k); }
$

During the link, ld emits a warning referencing _start1; it looks like ld f=
rom
binutils 2.18.5 gets into an infinite loop when performing a lookup in the
DWARF info:

(gdb) bt=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
#0  0x000d0c1c in add_line_info (table=3D0x207d4548, address=3D<optimized o=
ut>,
filename=3D0x201a80c0 "\001/usr/home/markj/src/freebsd-dev/lib/csu/i386", l=
ine=3D1,
    column=3D0, end_sequence=3D0) at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/dwarf2.c:849
#1  0x000cfd1e in decode_line_info (unit=3D<optimized out>, stash=3D<optimi=
zed
out>)
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/dwarf2.c:1169
#2  0x000cf693 in comp_unit_find_nearest_line (unit=3D0x207d44bc, addr=3D<o=
ptimized
out>, filename_ptr=3D0xffbfe5d0, functionname_ptr=3D0xffbfe5cc,
    linenumber_ptr=3D0xffbfe5c8, stash=3D0x20469e30)
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/dwarf2.c:2103=20
#3  0x000ced29 in find_line (abfd=3D0x201d50c0, section=3D<optimized out>,
offset=3D160, symbol=3D0x0, symbols=3D0x20480000, filename_ptr=3D0xffbfe5d0=
,=20=20=20=20=20=20=20=20=20=20=20=20
    functionname_ptr=3D0xffbfe5cc, linenumber_ptr=3D0xffbfe5c8, addr_size=
=3D0,
pinfo=3D0x20197344)=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/dwarf2.c:2575=20
#4  0x000ce063 in _bfd_dwarf2_find_nearest_line (abfd=3D0x201d50c0,
section=3D0x201990d0, symbols=3D0x20480000, offset=3D160, filename_ptr=3D0x=
ffbfe5d0,=20=20=20=20
    functionname_ptr=3D0xffbfe5cc, linenumber_ptr=3D0xffbfe5c8, addr_size=
=3D0,
pinfo=3D0x20197344)=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/dwarf2.c:2607=20
#5  0x000ac37e in _bfd_elf_find_nearest_line (abfd=3D0x201d50c0,
section=3D0x201990d0, symbols=3D0x20480000, offset=3D160, filename_ptr=3D0x=
ffbfe5d0,=20=20=20=20
    functionname_ptr=3D0xffbfe5cc, line_ptr=3D0xffbfe5c8)=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/elf.c:7198=20
#6  0x0007c3a9 in vfinfo (fp=3D0x181bac <__sF+472>, fmt=3D0x250e8 " undefin=
ed
reference to `%T'\n", arg=3D0xffbfe668 "\300P\035 \320\220\031 \240",
is_warning=3D1)=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/ld/../../../../contrib=
/binutils/ld/ldmisc.c:324=20
#7  0x0007c82d in einfo (fmt=3D0x250e3 "%X%C: undefined reference to `%T'\n=
")=20=20=20=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/ld/../../../../contrib=
/binutils/ld/ldmisc.c:465=20
#8  0x0007b838 in undefined_symbol (info=3D0x1831d0 <link_info>, name=3D0x2=
01bf6c8
"main", abfd=3D0x201d50c0, section=3D0x201990d0, address=3D160, error=3D1)=
=20=20=20=20=20=20=20=20=20=20=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/ld/../../../../contrib=
/binutils/ld/ldmain.c:1397=20
#9  0x0008f1d6 in elf_i386_relocate_section (output_bfd=3D0x201d5000,
info=3D0x1831d0 <link_info>, input_bfd=3D0x201d50c0, input_section=3D0x2019=
90d0,=20=20=20=20=20=20
    contents=3D0x206d5000
"1\355U\211\345\203\344\360\215E\b\203\354\004P\377u\004R\350\b",
relocs=3D0x201d8288, local_syms=3D0x2046be00,=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
    local_sections=3D0x201ff400) at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/elf32-i386.c:2346=20
#10 0x000bb38d in elf_link_input_bfd (input_bfd=3D<optimized out>,
finfo=3D<optimized out>)=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/elflink.c:8706=20
#11 bfd_elf_final_link (abfd=3D0x201d5000, info=3D0x1831d0 <link_info>)=20=
=20=20=20=20=20=20=20=20=20=20=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/libbfd/../../../../con=
trib/binutils/bfd/elflink.c:9843=20
#12 0x0007cf35 in ldwrite () at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/ld/../../../../contrib=
/binutils/ld/ldwrite.c:557=20
#13 0x0007a728 in main (argc=3D<optimized out>, argv=3D<optimized out>)=20=
=20=20=20=20=20=20=20=20=20=20=20=20
    at
/usr/home/markj/src/freebsd-dev/gnu/usr.bin/binutils/ld/../../../../contrib=
/binutils/ld/ldmain.c:468

The problem seems to occur only if crt1.o, which is a partial link of crt1_=
c.o
and crt1_s.o, is linked using lld. That is, if I link everything under lib/=
csu
using lld and just link crt1.o using ld.bfd, the infinite loop doesn't occu=
r.

If I try to link conftest.c using ld from binutils 2.30, I get an internal
warning instead of a hang:

$ clang conftest.c=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20
conftest.c:1:43: warning: control reaches end of non-void function
[-Wreturn-type]=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
int k; int foo () { __builtin_alloca (k); }=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20
                                          ^=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20
1 warning generated.=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
/usr/bin/ld: Dwarf Error: Line info data is bigger (0xefb0101) than the spa=
ce
remaining in the section (0x23f)
/usr/lib/crt1.o: In function `_start1':=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20
(.text+0xa0): undefined reference to `main'=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20
clang: error: linker command failed with exit code 1 (use -v to see invocat=
ion)
$

So it looks like lld is somehow messing up the DWARF info when merging crt1=
_c.o
and crt1_s.o.

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