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Differential D24348

ELF: clarify error when we don't know the output format
ClosedPublic

Authored by emaste on Sep 8 2016, 8:45 AM.

Details

Reviewers
ruiu
• rafael
Commits
rGe349b6da2c19: ELF: clarify error when we don't know the output format
rLLD280989: ELF: clarify error when we don't know the output format
rL280989: ELF: clarify error when we don't know the output format
Summary

lld differs from GNU ld in that it does not have a built-in default output emulation. It is always specified via the -m option or obtained from the object file(s) being linked. In most cases there is at least one ELF object in the link, so the emulation is known.

When using the WIP -b binary support (D24060) with -r to convert a binary file into an ELF object we do not have a known emulation. The error message previously emitted in this case "-m or at least a .o file required" is accurate but does not offer much insight. Add text to the error message indicating why -m or an object file is required.

Diff Detail

Repository
rL LLVM

Event Timeline

emaste updated this revision to Diff 70706.Sep 8 2016, 8:45 AM
emaste retitled this revision from to ELF: clarify error when we don't know the output format.
emaste updated this object.
emaste added reviewers: ruiu, • rafael.
emaste added a project: lld.
emaste added a subscriber: llvm-commits.
emaste mentioned this in D24060: [lld][ELF] Add support for -b binary.Sep 8 2016, 8:54 AM
emaste added a comment.Sep 8 2016, 8:56 AM

On second thought "format" is probably not right; the output is always ELF format.

"output target unknown"?
"output emulation unknown"?

emaste updated this revision to Diff 70743.Sep 8 2016, 12:53 PM
emaste added a subscriber: Bigcheese.

update message to one that matches lld --help terminology
-m <value> Set target emulation

davide added a subscriber: davide.Sep 8 2016, 12:57 PM

I find the message slightly more explicative, but I don't have a strong opinion on it.

ruiu accepted this revision.Sep 8 2016, 1:38 PM
ruiu edited edge metadata.

LGTM

This revision is now accepted and ready to land.Sep 8 2016, 1:38 PM
Closed by commit rL280989: ELF: clarify error when we don't know the output format (authored by emaste). · Explain WhySep 8 2016, 2:15 PM
This revision was automatically updated to reflect the committed changes.

Revision Contents

PathSize
lld/
trunk/
ELF/
2 lines
test/
ELF/
2 lines

Diff 70748

lld/trunk/ELF/Driver.cpp

Show First 20 Lines • Show All 307 Lines • ▼ Show 20 Lines case ELF32BEKind:
return; return;
case ELF64LEKind: case ELF64LEKind:
link<ELF64LE>(Args); link<ELF64LE>(Args);
return; return;
case ELF64BEKind: case ELF64BEKind:
link<ELF64BE>(Args); link<ELF64BE>(Args);
return; return;
default: default:
error("-m or at least a .o file required"); error("target emulation unknown: -m or at least one .o file required");
} }
} }
static UnresolvedPolicy getUnresolvedSymbolOption(opt::InputArgList &Args) { static UnresolvedPolicy getUnresolvedSymbolOption(opt::InputArgList &Args) {
if (Args.hasArg(OPT_noinhibit_exec)) if (Args.hasArg(OPT_noinhibit_exec))
return UnresolvedPolicy::Warn; return UnresolvedPolicy::Warn;
if (Args.hasArg(OPT_no_undefined) || hasZOption(Args, "defs")) if (Args.hasArg(OPT_no_undefined) || hasZOption(Args, "defs"))
return UnresolvedPolicy::NoUndef; return UnresolvedPolicy::NoUndef;
▲ Show 20 Lines • Show All 331 Lines • Show Last 20 Lines

lld/trunk/test/ELF/no-obj.s

// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
// RUN: llvm-ar rcs %t.a %t.o // RUN: llvm-ar rcs %t.a %t.o
// RUN: not ld.lld -o %t2 -u _start %t.a 2>&1 | FileCheck %s // RUN: not ld.lld -o %t2 -u _start %t.a 2>&1 | FileCheck %s
// CHECK: -m or at least a .o file required // CHECK: target emulation unknown: -m or at least one .o file required
.global _start .global _start
_start: _start: