Support for compiling to C/C++ header

[Themaister]

For many applications, it would be very convenient to be able to compile GLSL directly to a SPIR-V encoded as a static const uint32_t[].

In smaller projects, and especially for embedded/mobile, it is very useful to bake the SPIR-V shaders directly into the binary.

[dekimir]

Shaderc follows closely the glslang design here, and glslang only has functions to compile into a vector<unsigned int> for now.

[Themaister]

True, but emitting a C header is essentially just a different way of dumping the u32 vector to disk, so it shouldn't affect glslang at all. It is standalone enough that this could even be a separate binary.

[dekimir]

Sorry, I thought you were proposing a libshaderc interface extension. But it sounds like you just want to take the spv_binary and print its elements into a .h file? That's doable in ~4 lines of code, I think. Or are you proposing that we add a flag to glslc to do it automatically?

[Themaister]

I was thinking about adding some flags to glslc to dump out a header instead of raw .spv.
Again, trivial to do, but it's very convenient.

[dekimir]

@Themaister: makes sense. We'll come up with a suitable flag name and implement.

[dneto0]

I think we should mimic GCC's -masm=dialect option.
https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html#index-masm_003d_0040var_007bdialect_007d-2832

So you'd use -S to emit assembly and -masm=c to say you want C source.

One difficulty is in saying what variable name you want for the result. You might want to do this with several binaries.
So how about we just emit a brace-initialization list of values, and it's up to you to wrap the result.
eg. the output could be

  {  0x07230203, 0x00010000, 0x00080000, 1, 0 }

And you'd put that into a "binary.inc"
Then in your C code (or C++ code) you'd say

static uint32_t empty_binary[] = 
#include "binary.inc"
;

The point is that all the decisions about integrating it into the rest of your program are left to you, rather than adding lots of config parameters to glslc.

In this case I'd be tempted to use -masm=c-init-list as the option.

[Themaister]

That's a solid solution. It is indeed nice to avoid having to specify the array name on CLI, and it's also nice to avoid having to specify static/constness of the array in question. It can also be used as an initializer list in C++11 that way too.

[antiagainst]

#218 is landed. Closing.

[Themaister]

Works great. Thanks :)