[llvm-objdump] Invalid/Unsupported object file format

[CarlosAlbertoEnciso]

Using the given test case:

// test.cpp
int add(int First, int Second) {
  return First + Second;
}

and the command options:

clang -g -O0 --target=wasm64 -nostdlib -Wl,--no-entry -Wl,--export-all -o test.wasm test.cpp
llvm-objdump test.wasm --file-headers

it shows the error message

llvm-objdump: error: 'test.wasm': Invalid/Unsupported object file format

The error message is displayed for both targets wasm64 and wasm32.

However, other options such as: --disassemble, --headers, --full-contents recognize the format and display correct information.

[llvmbot]

@llvm/issue-subscribers-tools-llvm-objdump

Using the given test case: ``` // test.cpp int add(int First, int Second) { return First + Second; } ``` and the command options: ``` clang -g -O0 --target=wasm64 -nostdlib -Wl,--no-entry -Wl,--export-all -o test.wasm test.cpp llvm-objdump test.wasm --file-headers ``` it shows the error message ``` llvm-objdump: error: 'test.wasm': Invalid/Unsupported object file format ``` However, other options such as: `--disassemble, --headers, --full-contents` recognize the format and display correct information.

[CarlosAlbertoEnciso]

test.zip

[jh7370]

--file-headers isn't implemented in llvm-objdump for wasm currently (see

llvm-project/llvm/tools/llvm-objdump/llvm-objdump.cpp

Line 2861 in db777db

if (!O->isELF() && !O->isCOFF())

). Somebody like @sbc100 might be able to advise whether it's even applicable.

You can use llvm-readobj/llvm-readelf to dump the file header, but it looks like it just prints a version number.

[CarlosAlbertoEnciso]

Using wasm-objdump from the WebAssembly Binary Toolkit
https://github.com/WebAssembly/wabt

wasm-objdump test.wasm -h

test.wasm:	file format wasm 0x1
module name: <test.wasm>
Sections:
     Type start=0x0000000a end=0x00000014 (size=0x0000000a) count: 2
 Function start=0x00000016 end=0x00000019 (size=0x00000003) count: 2
   Memory start=0x0000001b end=0x0000001e (size=0x00000003) count: 1
   Global start=0x00000020 end=0x00000064 (size=0x00000044) count: 11
   Export start=0x00000067 end=0x00000124 (size=0x000000bd) count: 13
     Code start=0x00000126 end=0x0000016a (size=0x00000044) count: 2
   Custom start=0x0000016c end=0x000001bf (size=0x00000053) ".debug_abbrev"
   Custom start=0x000001c1 end=0x0000023c (size=0x0000007b) ".debug_info"
   Custom start=0x0000023f end=0x00000302 (size=0x000000c3) ".debug_str"
   Custom start=0x00000304 end=0x0000035b (size=0x00000057) ".debug_line"
   Custom start=0x0000035d end=0x000003a7 (size=0x0000004a) "name"
   Custom start=0x000003aa end=0x00000443 (size=0x00000099) "producers"
   Custom start=0x00000445 end=0x0000047b (size=0x00000036) "target_features"

I can be wrong, but just adding || Obj.isWasm() to

llvm-project/llvm/tools/llvm-objdump/llvm-objdump.cpp

Line 2861 in db777db

if (!O->isELF() && !O->isCOFF())

llvm-objdump is able to display the section headers:

test.wasm:	file format wasm
Sections:
Idx Name            Size     VMA              Type
  0 TYPE            0000000a 0000000000000000 
  1 FUNCTION        00000003 0000000000000000 
  2 MEMORY          00000003 0000000000000000 
  3 GLOBAL          00000044 0000000000000000 
  4 EXPORT          000000bd 0000000000000000 
  5 CODE            00000044 0000000000000000 TEXT
  6 .debug_abbrev   00000045 0000000000000000 
  7 .debug_info     0000006f 0000000000000000 
  8 .debug_str      000000b8 0000000000000000 
  9 .debug_line     0000004b 0000000000000000 
 10 name            00000045 0000000000000000 
 11 producers       0000008f 0000000000000000 
 12 target_features 00000026 0000000000000000 

[dschuff]

I think this is something that could be fixed straightforwardly.
Wasm has a file-level header (https://webassembly.github.io/spec/core/binary/modules.html#binary-module) that just has a magic number and a version number that has never changed. And then of course the list of sections, which each have their own header.

If we want to mirror the behavior for ELF, then maybe --file-headers should only print the file format and version? (and --section-headers should print that list of sections). WDYT?

[CarlosAlbertoEnciso]

@dschuff Thanks for the link on Wasm.
Your proposal seems good.

[llvmbot]

@llvm/issue-subscribers-backend-webassembly

Author: Carlos Alberto Enciso (CarlosAlbertoEnciso)

Using the given test case: ``` // test.cpp int add(int First, int Second) { return First + Second; } ``` and the command options: ``` clang -g -O0 --target=wasm64 -nostdlib -Wl,--no-entry -Wl,--export-all -o test.wasm test.cpp llvm-objdump test.wasm --file-headers ``` it shows the error message ``` llvm-objdump: error: 'test.wasm': Invalid/Unsupported object file format ``` The error message is displayed for both targets `wasm64` and `wasm32`.

However, other options such as: --disassemble, --headers, --full-contents recognize the format and display correct information.