Provided by: glslc_2024.3-1_amd64 
NAME
`glslc` - A command-line GLSL/HLSL to SPIR-V compiler with Clang-compatible arguments.
SYNOPSIS
glslc [--help]
glslc [-h]
glslc [--show-limits]
glslc [-c|-S|-E]
[-x ...] [-std=standard]
[ ... options for resource bindings ... ]
[-fhlsl-16bit-types]
[-fhlsl-offsets]
[-fhlsl-functionality1]
[-fentry-point=<name>]
[-fauto-map-locations]
[-finvert-y]
[-flimit=...]
[-flimit-file <resource-limits-file>]
[-fshader-stage=...]
[--target-env=...]
[--target-spv=...]
[-g]
[-O0|-Os]
[-Idirectory...]
[-Dmacroname[=value]...]
[-w] [-Werror]
[-o outfile]
shader...
DESCRIPTION
Input file languages
glslc accepts both GLSL/HLSL source and SPIR-V assembly files as inputs.
Shader stage specification
glslc provides three ways to specify the shader stage of a GLSL source file:
-fshader-stage=<stage>, #pragma shader_stage(<stage>), and file extension. The
-fshader-stage= option overrides #pragma shader_stage(), which overrides the file
extension.
Shader stages can be specified by naming a file with an appropriate extension as shown in
the following table. -fshader-stage= and #pragma shader_stage(), on the other hand, enable
you to specify shader stages from the command line and within the source file. Possible
stages for them are also listed in the following table. Details about -fshader-stage= can
be found in its own section.
Table 1. Shader Stage Selection
┌───────────────────────┬───────────────────────┬─────────────┐
│ │ │ │
│Shader Stage │ Shader File Extension │ <stage> │
├───────────────────────┼───────────────────────┼─────────────┤
│ │ │ │
│vertex │ .vert │ vertex │
├───────────────────────┼───────────────────────┼─────────────┤
│ │ │ │
│fragment │ .frag │ fragment │
├───────────────────────┼───────────────────────┼─────────────┤
│ │ │ │
│tesselation control │ .tesc │ tesscontrol │
├───────────────────────┼───────────────────────┼─────────────┤
│ │ │ │
│tesselation evaluation │ .tese │ tesseval │
├───────────────────────┼───────────────────────┼─────────────┤
│ │ │ │
│geometry │ .geom │ geometry │
├───────────────────────┼───────────────────────┼─────────────┤
│ │ │ │
│compute │ .comp │ compute │
└───────────────────────┴───────────────────────┴─────────────┘
#pragma shader_stage() relies on the #pragma preprocessor directive; thus, the token
inside shader_stage() is not subject to preprocessor macro expansion. It must be exactly
one of the stages in the above table.
#pragma shader_stage() behaves as follows:
• The first #pragma shader_stage() directive in a translation unit must precede any
non-preprocessor tokens.
• If there is more than one #pragma shader_stage() directive in the same translation
unit, all the stages specified must be the same. Otherwise, glslc will issue an error.
SPIR-V assembly files
SPIR-V assembly input files should follow the syntax
<https://github.com/KhronosGroup/SPIRV-Tools/blob/master/syntax.md> defined in the
SPIRV-Tools <https://github.com/KhronosGroup/SPIRV-Tools> project and have the .spvasm
extension. Command line options treat SPIR-V assembly files differently; some may ignore
them, e.g., -E, -S, and some may even treat them not as SPIR-V assembly files, e.g.,
-fshader-stage=.
Output file naming
If a name is specified via -o, the output file will be given that name. Otherwise,
• If a compilation stage selection option is given (-S or -c), there will be one output
file generated per input shader file. The generated output file will end with a file
extension that matches the compilation stage, which is .spvasm for -S and .spv for -c.
The name will depend on the original file’s name and extension.
• If the input file has a shader stage selection extension, the output file will be
named as by appending the file extension for the compilation stage to the input
file’s name. E.g., glslc -c foo.vert will generate foo.vert.spv, and glslc -S
bar.frag will generate bar.frag.spvasm.
• Otherwise, the output file will be named as by replacing the input file’s file
extension, if any, with the file extension for the compilation stage. E.g., glslc
-c foo will generate foo.spv, and glslc -S bar.glsl will generate bar.spvasm.
• If no compilation stage is selected, the output file will be named a.spv.
COMMAND LINE OPTIONS
Overall Options
--help, -h
Option --help or -h tells the glslc compiler to display all available options and exit.
--show-limits
--show-limits shows default resource limits for shader compilation. The syntax is the same
as accepted by -flimit= and for the contents of the file specified by -flimit-file.
-o
-o lets you specify the output file’s name. It cannot be used when there are multiple
files generated. A filename of - represents standard output.
Language and Mode Selection Options
-finvert-y
Inverts position.Y output in a vertex shader.
-flimit=
-flimit=<resource-limits> lets you specify resource limits. The argument should be a
sequence of limit name, integer value pairs. Tokens should be separated by whitespace. If
the same limit is specified several times, only the last setting takes effect.
Use --show-limits to show the default values, and example syntax.
This option affects all compiled shaders.
-flimit-file
-flimit-file <resource-limits-file> lets you specify resource limits in a file. The syntax
of the file contents is the same as the argument to -flimit= and the output of
--show-limits. This option accepts Glslang resource configuration files, e.g. as emitted
by glslangValidator -c.
This option affects all compiled shaders.
-fshader-stage=
-fshader-stage=<stage> lets you specify the shader stage for one or more inputs from the
command line.
Possible values for <stage> are listed in the Shader Stage Selection table.
-fshader-stage= behaves as follows:
• -fshader-stage= sets the shader stage for subsequent input files. It does not affect
the stages of any preceding inputs on the command line.
• When supplying more than one -fshader-stage= argument, the most recent argument
preceding an input file applies.
• A shader file not ending with known shader file extensions must have a -fshader-stage=
argument ahead of it to specify its stage.
• If there is a -fshader-stage= before a file in which there is a #pragma shader_stage()
directive, the directive is ignored and the -fshader-stage= argument is used instead.
• If there is a -fshader-stage= before a file with a known shader file extension, the
file extension is ignored and the -fshader-stage= argument is used instead.
Caution
-fshader-stage= overrides file extension; that means it should not be used together
with SPIR-V assembly files because glslc will treat the given SPIR-V assembly files as
GLSL source code of the given shader stage. If you need to supply both SPIR-V assembly
files and -fshader-stage= on the same command line, please put SPIR-V assembly files
ahead of the first -fshader-stage=, since -fshader-stage= only affects the treatment
of subsequent files.
-std=
-std=<value> lets you specify a shader version and profile on the command line. <value>
can be any valid concatenation of a GLSL version number and profile, e.g., 310es, 450core,
etc. The profile can be omitted as allowed by GLSL, e.g., 450.
-std= behaves as follows:
• -std= affects the version of all GLSL inputs passed to glslc.
• -std= is ignored for HLSL inputs.
• -std= overwrites #version directives in all input shaders, including those preceding
the argument.
• If a -std= argument specifies a different version from a #version directive in an
input file, glslc will issue a warning.
• If multiple -std= arguments are specified on the command line, only the last one takes
effect.
Caution
-std= does not affect the #version directive in the preprocessed output. That is, when
-std= specifies a version different from the shader source code, the #version
directive in preprocessed output will still be the one in the source code. But -std=
does affect the behavior of #line directives in the preprocessed output. Behavior of
#line directives will follow the version specified by -std=.
--target-env=
--target-env=<value> lets you specify a target environment on the command line. This
affects the generation of warnings and errors. The <value> can be one of the following:
• vulkan: create SPIR-V under Vulkan 1.0 semantics.
• vulkan1.0: create SPIR-V under Vulkan 1.0 semantics.
• vulkan1.1: create SPIR-V under Vulkan 1.1 semantics.
• vulkan1.2: create SPIR-V under Vulkan 1.2 semantics.
• opengl: create SPIR-V under OpenGL 4.5 semantics.
• opengl4.5: create SPIR-V under OpenGL 4.5 semantics.
Generated code uses SPIR-V 1.0, except for code compiled for Vulkan 1.1, which uses SPIR-V
1.3, and code compiled for Vulkan 1.2, which uses SPIR-V 1.5.
If this option is not specified, a default of vulkan1.0 is used.
Note: Support for OpenGL compatibility profile, opengl_compat, has been removed.
--target-spv=
--target-spv=<value> lets you specify the SPIR-V version to be used by the generated
module. The default is to use the highest version of SPIR-V required to be supported by
the target environment. The defaults for specific Vulkan target environments are as
follows: SPIR-V 1.0 for Vulkan 1.0, SPIR-V 1.3 for Vulkan 1.1, and SPIR-V 1.5 for Vulkan
1.2.
The <value> can be one of the following:
• spv1.0
• spv1.1
• spv1.2
• spv1.3
• spv1.4
• spv1.5
• spv1.6
-x
-x lets you specify the language of the input shader files. Valid languages are glsl and
hlsl. If the file extension is hlsl then the default language is HLSL. Otherwise the
default is 'glsl'.
Note: HLSL compilation will use HLSL packing (offset) rules for variables that are vertex
shader outputs, and inputs and outputs of both geometry and pixel shaders.
Compilation Stage Selection Options
-c
-c tells the glslc compiler to run the preprocessing and compiling stage. Each input
shader file results in a SPIR-V binary file; these SPIR-V binary files are named by the
rules in the Output File Naming section.
-E
-E tells the glslc compiler to run only the preprocessing stage. It overrides -c and -S.
Preprocessed output is written to standard output, while preprocessing errors are written
to standard error. If multiple input shader files are given, their preprocessed output are
all written to standard output, in the order specified on the command line.
glslc will do nothing for SPIR-V assembly files with this option.
-S
-S tells the glslc compiler to run the preprocessing, compiling, and then disassembling
stage. It overrides -c. Each input shader file results in a SPIR-V assembly file; these
SPIR-V assembly files are named by the rules in the Output File Naming section.
glslc will do nothing for SPIR-V assembly files with this option.
No Compilation Stage Selection
If none of the above options is given, the glslc compiler will run preprocessing,
compiling, and linking stages.
Warning
Linking of multiple input shader files are not supported yet.
Preprocessor Options
-D
-Dmacroname[=[value]] lets you define a preprocessor macro before input shader files are
preprocessed. If value is omitted, the macro is defined with an empty value.
-I
-Idirectory or -I directory adds the specified directory to the search path for include
files. The directory may be an absolute path or a relative path to the current working
directory.
Code Generation Options
-g
Requests that the compiler place source-level debug information into the object code, such
as identifier names and line numbers.
This option restrains -O from turning on the strip-debug-info optimization pass.
Note
Currently this option has no effect. Full functionality depends on glslang support for
generating debug info.
-O0, -Os
-O specifies which optimization level to use:
• -O0 means "no optimization". This level generates the most debuggable code.
• -O means the default optimization level for better performance.
• -Os enables optimizations to reduce code size.
-mfmt=<format>
-mfmt=<format> selects output format for compilation output in SPIR-V binary code form.
Supported options are listed in the binary output format options table. This option is
only valid to be used when the compilation output is SPIR-V binary code. Specifying any
options listed below when the output is not SPIR-V binary code, like disassembly (with -S
specified), text (with -M, -MM or -E specified) will trigger an error.
Table 2. Binary Output Format Options
┌──────────────┬────────────────────────────────────────────────┐
│ │ │
│Format option │ Description │
├──────────────┼────────────────────────────────────────────────┤
│ │ │
│bin │ Output SPIR-V binary code as a │
│ │ sequence of binary 32-bitwords │
│ │ in host native endianness. This │
│ │ is the default format for SPIR-V │
│ │ binary compilation output. │
├──────────────┼────────────────────────────────────────────────┤
│ │ │
│num │ Output SPIR-V binary code as a │
│ │ text file containing a list of │
│ │ comma-separated hex numbers. │
│ │ Example: glslc -c -mfmt=num │
│ │ main.vert -o output_file.txt │
│ │ Content of the output_file.txt: │
│ │ 0x07230203,0x00010000,0x00080001,0x00000006... │
├──────────────┼────────────────────────────────────────────────┤
│ │ │
│c │ Output SPIR-V binary code as a text file │
│ │ containing C-style │
│ │ initializer list. │
│ │ This is just wrapping the output of num option │
│ │ with curly brackets. │
│ │ Example: glslc -c -mfmt=c main.vert -o │
│ │ output_file.txt │
│ │ Content of output_file.txt: │
│ │ {0x07230203, 0x00010000, 0x00080001, │
│ │ 0x00000006...} │
└──────────────┴────────────────────────────────────────────────┘
-fhlsl-16bit-types
Enables 16bit types for HLSL compilation.
-fhlsl-offsets
Use HLSL packing rules instead of GLSL rules when determining offsets of members of
blocks. This option is always on when compiling for HLSL.
-fhlsl-functionality1
Enable extension SPV_GOOGLE_hlsl_functionality1, and instructs the compiler to:
• Annotate HLSL semantic string decorations on interface objects
• Explicitly record the association of a UAV resource with its companion counter buffer.
This option can also be spelled with an underscore: -fhlsl_functionality1.
-fentry-point=<name>
-fentry-point=<name> lets you specify the entry point name. This is only significant for
HLSL compilation. The default is "main".
-fauto-map-locations
For GLSL compilation, option -fauto-map-locations directs the compiler to automatically
assign location numbers to user-defined stage input and output variables if not explicitly
specified by the shader source.
For HLSL compilation, this option is on by default.
Client APIs normally require adjacent stages to agree on their I/O interface. The compiler
only sees one stage at a time, so it is strongly recommended that you avoid relying on
this option to assign locations.
Instead, an explicit binding number should be specified in the shader source, as follows:
• In a GLSL shader, use a location layout qualifier:
layout(location = 1) in vec4 x;
• In an HLSL shader, use a vk::location attribute:
[[vk::location(1)]] float4 FooShader(
[[vk::location(0)]] float4 a,
[[vk::location(2)]] float4 b) : COLOR0 {
return a + b;
}
[[option-fpreserve-bindings ==== -fpreserve-bindings
Directs the optimizer to preserve bindings declarations, even when those bindings are
known to be unused.
Warning and Error Options
-w
-w suppresses all warning output from glslc. Any warning that would have been generated is
silently ignored.
-Werror
-Werror forces any warning to be treated as an error in glslc. This means that all
warning: messages are shown as error: and any warnings will cause a non-zero exit code
from glslc. If -w is specified the warnings generated are suppressed before they are
converted to errors.
Dependency Generation Options
-M or -MM
-M generates make dependencies. It outputs a rule suitable for make describing the
dependencies of the input file. Instead of outputting the result of preprocessing, the
preprocessor outputs one make rule containing the SPIR-V object file name for that source
file, a colon, and the names of all the included files.
Unless specified explicitly (with -MT), the SPIR-V object file name in the generated make
rules follows the rules of Output File Naming as in -c compilation stage.
Specifying -M implies -E, and suppresses warnings with an implicit -w. By default the
output will be written to stdout, unless -MF or -o is specified.
The dependency info file name can be specified by -o and -MF options. When both are
specified, -o option is ignored.
Specifying multiple input files is valid when the make rules are written to stdout, which
means neither -MF nor -o is specified. When -o or -MF is specified, only one input file is
allowed.
-MM is an alias for -M.
E.g., glslc -M main.vert will dump main.vert.spv: main.vert <other included files> to
stdout. More examples are listed in Dependency Generation Examples
-MD
-MD tells the glslc compiler to both compile the source and generate make dependencies.
Dependencies are written to a file whose name is determined as follows: If option -MF is
specified, use its argument. Otherwise, use the filename formed by appending .d to the
name of the file containing compilation results.
Specifying multiple input files is valid when neither -MF nor -o is specified. When -o or
-MF is specified, only one input file is allowed.
E.g., glslc -c -MD main.vert will generate main.vert.spv as the SPIR-V object file and
main.vert.spv.d as the dependency info file. More examples are listed in Dependency
Generation Examples
-MF
-MF lets you specify the dependency info file name when used with -M or -MD. This option
is invalid when used with multiple input files.
E.g., glslc -c -MD main.vert -MF dep_info will generate main.vert.spv as the SPIR-V object
file and dep_info as the dependency info file.
-MT
-MT lets you specify the target of the rule emitted by dependency generation when used
with -M or -MD. This option is invalid when used with multiple input files.
E.g., glslc -M main.vert -MT target will dump following dependency info to stdout: target:
main.vert <other dependent files>.
Table 3. Dependency Generation Examples
┌────────────────────┬────────────────────┬────────────────────┬────────────────────┐
│ │ │ │ │
│Command Line Input │ Compilation Output │ Dependency Output │ Dependency Info │
│ │ File │ File │ │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -M main.vert │ <NA> │ <Stdout> │ main.vert.spv: │
│ │ │ │ main.vert │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -M a.vert │ <NA> │ <Stdout> │ a.vert.spv: a.vert │
│b.vert │ │ │ │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│ │ <NA> │ <Stdout> │ b.vert.spv: b.vert │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -M main.vert │ <NA> │ dep_info │ main.vert.spv: │
│-o dep_info │ │ │ main.vert │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -M main.vert │ <NA> │ dep_info │ main.vert.spv: │
│-MF dep_info │ │ │ main.vert │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -M main.vert │ <NA> │ <Stdout> │ target: main.vert │
│-MT target │ │ │ │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -MD main.vert │ a.spv │ main.vert.spv.d │ main.vert.spv: │
│ │ │ │ main.vert │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -c -MD │ main.vert.spv │ main.vert.spv.d │ main.vert.spv: │
│main.vert │ │ │ main.vert │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -c -MD a.vert │ a.vert.spv │ a.vert.spv.d │ a.vert.spv: a.vert │
│b.vert │ │ │ │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│ │ b.vert.spv │ b.vert.spv.d │ b.vert.spv: b.vert │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -S -MD │ main.vert.spvasm │ main.vert.spvasm.d │ main.vert.spvasm: │
│main.vert │ │ │ main.vert │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -c -MD │ main.vert.spv │ dep_info │ main.vert.spv: │
│main.vert -MF │ │ │ main.vert │
│dep_info │ │ │ │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -c -MD │ obj │ obj.d │ obj: main.vert │
│main.vert -o obj │ │ │ │
├────────────────────┼────────────────────┼────────────────────┼────────────────────┤
│ │ │ │ │
│glslc -c -MD │ obj │ dep_info │ target: main.vert │
│main.vert -o obj │ │ │ │
│-MF dep_info -MT │ │ │ │
│target │ │ │ │
└────────────────────┴────────────────────┴────────────────────┴────────────────────┘
Resource Binding Options
-fauto-bind-uniforms
Option -fauto-bind-uniforms directs the compiler to automatically assign binding numbers
to uniform variables, when an explicit binding is not specified in the shader source.
An explicit binding number can be specified in the shader source by using a binding layout
qualifier. For example:
layout(binding = 12) uniform texture2D;
-fhlsl-iomap
Option -fhlsl-iomap directs the compiler to use HLSL register assignments as binding
values.
-fimage-binding-base
Option -fimage-binding-base [stage] base sets the lowest automatically assigned binding
for images. If a stage is specified, only affects the specified stage.
For HLSL, sets one less than the base.
-fsampler-binding-base
Option -fsampler-binding-base [stage] base sets the lowest automatically assigned binding
for samplers. If a stage is specified, only affects the specified stage.
For HLSL, sets one less than the base.
-ftexture-binding-base
Option -ftexture-binding-base [stage] base sets the lowest automatically assigned binding
for textures. If a stage is specified, only affects the specified stage.
For HLSL, sets one less than the base.
-fubo-binding-base
Option -fubo-binding-base [stage] base sets the lowest automatically assigned binding for
Uniform Buffer Objects (GLSL) or Cbuffers (HLSL). If a stage is specified, only affects
the specified stage.
For HLSL, sets one less than the base.
-fcbuffer-binding-base
Option -fcbuffer-binding-base [stage] base is the same as -fubo-binding-base [stage] base.
-fssbo-binding-base
Option -fssbo-binding-base [stage] base sets the lowest automatically assigned binding for
Shader Storage Buffer Objects (GLSL). If a stage is specified, only affects the specified
stage.
This only affects GLSL compilation.
-fuav-binding-base
Option -fuav-binding-base [stage] base sets one less than the lowest automatically
assigned binding for Unordered Access Views (UAV). If a stage is specified, only affects
the specified stage.
This only affects HLSL compilation.
-fresource-set-binding
Option -fresource-set-binding [stage] <reg0> <set0> <binding0> sets the descriptor set and
binding for an HLSL resource, by register name. To specify settings for more registers,
append their triples consisting of register name, descriptor set, and binding.
Example:
# For a texture in register t1, use set 1 binding 0.
# For a texture in register t2, use set 1 binding 3
glslc -x hlsl foo.frag -fresource-set-binding t1 1 0 t2 1 3
If a stage is specified, only affects the specified stage.
# Same as the previous example, but the settings only apply
# to fragment (pixel) shaders.
glslc -x hlsl foo.frag -fresource-set-binding frag t1 1 0 t2 1 3
DIVERGENCE FROM AND EXTENSIONS TO GLSL SPECIFICATIONS
Source-filename-based #line and __FILE__
This section describes how the glslc compiler extends the syntax for the #line directive
and the __FILE__ macro. By default, the glslc compiler enables the
GL_GOOGLE_cpp_style_line_directive extension. It will generate this extended syntax in the
preprocessed output (obtained via the -E option).
Warning
This section is still evolving. Expect changes.
GLSL specifications have a notion of source strings.
The source for a single shader is an array of strings of characters from the
character set. A single shader is made from the concatenation of these strings.
— Section 3.2 of both version 3.30 and 4.50
With the above notion, the second parameter to the #line directive should be a constant
integer expressions representing the source string number. Also the __FILE__ macro will
"substitute a decimal integer constant that says which source string number is currently
being processed."
The glslc compiler implements the standard #line and __FILE__ syntax. It also provides an
extension, GL_GOOGLE_cpp_style_line_directive, to allow source filenames to be used
instead of integer source string indices. Specifically, the #line directive can have,
after macro substitution, one of the following three forms:
#line line-number
#line line-number integer-source-string-index
#line line-number "source-filename"
where source-filename can be any combinations of characters except double quotation marks.
(Note that according to the GLSL specification, "there are no escape sequences or other
uses of the backslash beyond use as the line-continuation character".)
And if source-filename-based #line is used, the __FILE__ macro expands to a string whose
contents are the filename quoted with double quotation marks. The filename is dertermined
as the last of
• The filename given to the glslc compiler,
• The filename argument of the most recent #line directive, if any.
#include
The glslc compiler extends GLSL with the include syntax by turning on the
GL_GOOGLE_include_directive extension. It will preprocess and substitute #include
directives properly with the following behaviors.
Warning
This section is still evolving. Expect changes.
If #include directives are used in a shader, there will be an #extension
GL_GOOGLE_include_directive : enable line generated into the preprocessed output.
The GL_GOOGLE_cpp_style_line_directive extension is implicitly turned on by the
GL_GOOGLE_include_directive extension.
The file argument to #include must be enclosed in double quotes. It must be a relative
path, using whatever path separator the OS supports. However, the last path element — the
name of the file itself — must not contain either '/' or '\', regardless of which path
separator is used. This will not be flagged as an error but will instead trigger undefined
behavior. For example, let’s say there is a file named f\ilename.vert on a Unix OS. It is
not possible to craft a #include that includes that file.
Furthermore, it is not possible to escape any characters in a #include directive, so the
file argument cannot contain any special characters that need escaping in C.
The file argument is a relative path that is matched first against the including file’s
own directory and then against all -I arguments in order of their appearance on the
command line. If the file cannot be found, glslc aborts with an error.
2024-09-28 `GLSLC`(1)