# ArgumentError: embedded NULs are not allowed in C strings:

[zygmuntszpak]

Hi,
I'm having trouble figuring out how to use CImGui.InputText(). The examples in the demo work correctly, but whenever I try to incorporate something similar I encounter an embedded NULs are not allowed in C strings: error. For example, the following does not work

        buf="dummy"*"\0"^(27) 
        CImGui.InputText("dummy", buf, length(buf))  # ArgumentError: embedded NULs are not allowed in C strings

I've made a standalone script which attempts to imitate an example in the demos:

using CImGui
using CImGui.CSyntax
using CImGui.CSyntax.CStatic
using CImGui.GLFWBackend
using CImGui.OpenGLBackend
using CImGui.GLFWBackend.GLFW
using CImGui.OpenGLBackend.ModernGL
using Printf


@static if Sys.isapple()
    # OpenGL 3.2 + GLSL 150
    glsl_version = 150
    GLFW.WindowHint(GLFW.CONTEXT_VERSION_MAJOR, 3)
    GLFW.WindowHint(GLFW.CONTEXT_VERSION_MINOR, 2)
    GLFW.WindowHint(GLFW.OPENGL_PROFILE, GLFW.OPENGL_CORE_PROFILE) # 3.2+ only
    GLFW.WindowHint(GLFW.OPENGL_FORWARD_COMPAT, GL_TRUE) # required on Mac
else
    # OpenGL 3.0 + GLSL 130
    glsl_version = 130
    GLFW.WindowHint(GLFW.CONTEXT_VERSION_MAJOR, 3)
    GLFW.WindowHint(GLFW.CONTEXT_VERSION_MINOR, 0)
    # GLFW.WindowHint(GLFW.OPENGL_PROFILE, GLFW.OPENGL_CORE_PROFILE) # 3.2+ only
    # GLFW.WindowHint(GLFW.OPENGL_FORWARD_COMPAT, GL_TRUE) # 3.0+ only
end

# setup GLFW error callback
error_callback(err::GLFW.GLFWError) = @error "GLFW ERROR: code $(err.code) msg: $(err.description)"
GLFW.SetErrorCallback(error_callback)

# create window
window = GLFW.CreateWindow(1280, 720, "Demo")
@assert window != C_NULL
GLFW.MakeContextCurrent(window)
GLFW.SwapInterval(1)  # enable vsync

# setup Dear ImGui context
ctx = CImGui.CreateContext()

# setup Dear ImGui style
CImGui.StyleColorsDark()

# setup Platform/Renderer bindings
ImGui_ImplGlfw_InitForOpenGL(window, true)
ImGui_ImplOpenGL3_Init(glsl_version)
should_show_dialog = true
clear_color = Cfloat[0.45, 0.55, 0.60, 1.00]
current_path = pwd()
while !GLFW.WindowShouldClose(window)

    GLFW.PollEvents()
    # start the Dear ImGui frame
    ImGui_ImplOpenGL3_NewFrame()
    ImGui_ImplGlfw_NewFrame()
    CImGui.NewFrame()

    # ArgumentError: embedded NULs are not allowed in C strings:
    @cstatic buf="dummy"*"\0"^(27) begin
        CImGui.InputText("1", buf, length(buf))
    end

    # rendering
    CImGui.Render()
    GLFW.MakeContextCurrent(window)
    display_w, display_h = GLFW.GetFramebufferSize(window)
    glViewport(0, 0, display_w, display_h)
    glClearColor(clear_color...)
    glClear(GL_COLOR_BUFFER_BIT)
    ImGui_ImplOpenGL3_RenderDrawData(CImGui.GetDrawData())

    GLFW.MakeContextCurrent(window)
    GLFW.SwapBuffers(window)
end

# cleanup
ImGui_ImplOpenGL3_Shutdown()
ImGui_ImplGlfw_Shutdown()
CImGui.DestroyContext(ctx)

GLFW.DestroyWindow(window)

This error is as follows:

ERROR: LoadError: ArgumentError: embedded NULs are not allowed in C strings: "dummy\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
Stacktrace:
 [1] igInputText(::String, ::String, ::Int64, ::Int64, ::Ptr{Nothing}, ::Ptr{Nothing}) at ./c.jl:216
 [2] InputText at /home/zygmunt/.julia/packages/CImGui/PuVOE/src/wrapper.jl:1298 [inlined] (repeats 2 times)
 [3] top-level scope at /home/zygmunt/.julia/dev/ElectrodermalActivity/src/standalone.jl:59 [inlined]
 [4] top-level scope at ./none:0
in expression starting at /home/zygmunt/.julia/dev/ElectrodermalActivity/src/standalone.jl:49

I suspect that I am using the API incorrectly. I haven't yet worked with a scenario where I was passing data structures to a C-library so I'd appreciate any suggestions you may have.

[zygmuntszpak]

Here is how I worked around the problem. I have three working solutions, but I am not sure which (if any) are "permissible". I would go with option 3 because it is the shortest:

        # Solution 1
        str = "dummy"*"\0"^(27)
        buf = Cstring(Base.unsafe_convert(Ptr{Cchar}, str))
        CImGui.InputText("Label 1",buf, length(str))
        @show str

        # Solution 2
        str2 =  "dummy"*"\0"^(27)
        buf2 = Cstring(pointer(Base.cconvert(Ptr{Cchar}, str2)))
        CImGui.InputText("Label 2",buf2, length(str2))
        @show str2

        # Solution 3
        str3 =  "dummy"*"\0"^(27)
        buf3 = Cstring(pointer(str3))
        CImGui.InputText("Label 3",buf3, length(str3))
        @show str3

[Gnimuc]

Sorry, that's an upgrading flaw due to this commit.

[Gnimuc]

Thanks for the feedback! I'm going to tag a new version.

[wdevore]

Here is how I worked around the problem. I have three working solutions, but I am not sure which (if any) are "permissible". I would go with option 3 because it is the shortest:

        # Solution 1
        str = "dummy"*"\0"^(27)
        buf = Cstring(Base.unsafe_convert(Ptr{Cchar}, str))
        CImGui.InputText("Label 1",buf, length(str))
        @show str

        # Solution 2
        str2 =  "dummy"*"\0"^(27)
        buf2 = Cstring(pointer(Base.cconvert(Ptr{Cchar}, str2)))
        CImGui.InputText("Label 2",buf2, length(str2))
        @show str2

        # Solution 3
        str3 =  "dummy"*"\0"^(27)
        buf3 = Cstring(pointer(str3))
        CImGui.InputText("Label 3",buf3, length(str3))
        @show str3

Weird. I get the opposite. The examples get an error and I don't know how to fix it. I am on a linux box with julia 1.1.0. I will try one of zygmuntszpak solutions.

Update: I upgraded to 1.69.1 and the issue is fixed. ;-)