[Bug build/26559] New: Get OUTPUT_FORMAT from objdump -f to support LLD

[Bug build/26559] New: Get OUTPUT_FORMAT from objdump -f to support LLD

[i at maskray dot me]

https://sourceware.org/bugzilla/show_bug.cgi?id=26559

            Bug ID: 26559
           Summary: Get OUTPUT_FORMAT from objdump -f to support LLD
           Product: glibc
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: build
          Assignee: unassigned at sourceware dot org
          Reporter: i at maskray dot me
                CC: carlos at redhat dot com
  Target Milestone: ---

OUTPUT_FORMAT is needed as the first line of libc.so (a linker script). The
string comes from either

(a) ld --verbose on /dev/null, get the output (the OUTPUT_FORMAT line and the
continuation lines), feed the output to scripts/output-format.sed
(b) ld --print-output-format

Neither choice makes sense for LLD. It supports multi targets and there is not
a preferred default target. Like gold, it does not have the concept of "an
internal linker script". ld.lld --verbose does not print OUTPUT_FORMAT.

As an alternative, we can get the string from objdump -f

```
% objdump -f /lib/x86_64-linux-gnu/libc.so.6 

/lib/x86_64-linux-gnu/libc.so.6:     file format elf64-x86-64

# LLVM>=11.0.0 (since https://reviews.llvm.org/D76046 )
% llvm-objdump -f /lib/x86_64-linux-gnu/libc.so.6

/lib/x86_64-linux-gnu/libc.so.6:        file format elf64-x86-64

architecture: x86_64
start address: 0x0000000000026e00
```

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[Bug build/26559] Get OUTPUT_FORMAT from objdump -f to support LLD

[i at maskray dot me]

https://sourceware.org/bugzilla/show_bug.cgi?id=26559

Fangrui Song <i at maskray dot me> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |26558


Referenced Bugs:

https://sourceware.org/bugzilla/show_bug.cgi?id=26558
[Bug 26558] [meta] Build glibc with LLD
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[Bug build/26559] Get OUTPUT_FORMAT from objdump -f to support LLD

[i at maskray dot me]

https://sourceware.org/bugzilla/show_bug.cgi?id=26559

Fangrui Song <i at maskray dot me> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #1 from Fangrui Song <i at maskray dot me> ---
Fixed by
https://sourceware.org/git/?p=glibc.git;a=commit;h=02d393f2483aedc4ce74e6edf8a15f063198041d
("install: Replace scripts/output-format.sed with objdump -f [BZ #26559]") a
while ago.

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