[cmake-developers] [PATCH for bug 15253] Ninja: Pass only the flags relevant to the language.

[Brian Smith]

Brad King <brad.king at kitware.com> wrote:
> The original issue could have been worded to explain that nasm/yasm
> dependencies are not handled correctly, so I'd like to treat it that
> way.

OK.

> If these tools have the -M flag then a "deptype = gcc" code path
> should work.

yasm has an -M flag that causes it to write the dependencies to stdout
WITHOUT doing the assembly. nasm additionally has -MD <file>, which
causes it to write the dependencies to <file> AND do the assembly.
yasm does NOT have -MD. I don't see how to make CMake execute yasm -M
-o <x>.obj <x>.asm > $DEP_FILE and then execute yasm -o <x>.obj
<x>.asm to do the actual assembly.

Instead, I decided to try to add -MD to yasm. See the attached patch,
which is a very rough draft.

> The usingMSVC boolean should be updated to be false
> for lang != C|CXX|RC so that the "else" code path is taken.  Then
>
>  CMAKE_DEPFILE_FLAGS_<LANG>
>
> should be added to the platform modules for these toolchains.

I think I understood what you meant, and I've attached a patch that does that.

With my patch, cmake -GNinja generates a rule like this:

rule ASM_NASM_COMPILER
  depfile = $DEP_FILE
  deps = gcc
  command = c:\<path-to-yasm>yasm.exe  $FLAGS -MD $DEP_FILE -f win32 -o $out $in
  description = Building ASM_NASM object $out

That looks right to me.

But, when I execute ninja and it executes the rule, it never provides
a value for $DEP_FILE. Instead, the executed command looks like this:

10/358] Building ASM_NASM object cryp...\CMakeFiles\sha.dir\sha512-586.asm.obj
FAILED: c:\<path-to-yasm>\yasm.exe  -I..\crypto\.
-I..\crypto\..\include -I..\crypto\sha\. -I..\crypto\sha\..
-I..\crypto\sha\..\..\include -MD  -f win32 -o
crypto\sha\CMakeFiles\sha.dir\sha512-586.asm.obj crypto\sh
\sha512-586.asm
asm: option `-MD' needs an argument!

Notice that the empty string was substituted for $DEP_FILE.

It seems like solving this requires more understanding of how CMake
works than I currently have. Any ideas?

Thanks for your help on this.

Cheers,
Brian
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