Strdup undeclared under MinGW with -std=c++11 in imgui_demo

[Teybeo]

Hi,
I just decided to give a try to this lib as it looks super cool and I only encoutered one compilation error so I though I should report it before forgetting about it 😃

In Clion, after copying and defining all the root files in the CMakeLists.txt, i got these errors:

D:\Dev\Sandbox\Imgui demo\imgui_demo.cpp: In member function 'void ExampleAppConsole::AddLog(const char*, ...)':
D:\Dev\Sandbox\Imgui demo\imgui_demo.cpp:1874:37: error: 'strdup' was not declared in this scope
         Items.push_back(strdup(buf));
                                     ^
D:\Dev\Sandbox\Imgui demo\imgui_demo.cpp: In member function 'void ExampleAppConsole::ExecCommand(const char*)':
D:\Dev\Sandbox\Imgui demo\imgui_demo.cpp:1967:48: error: 'strdup' was not declared in this scope
         History.push_back(strdup(command_line));
                                                ^

My env is MinGW on Win7 with GCC 4.8.1
This function seems to be from POSIX standard but not from C/C++.

Looking at the code I found the ImStrdup() function declared in imgui_internal.h and defined in imgui.cpp.
Changing the 2 strdup to ImStrdup and adding #include "imgui_internal.h" in imgui_demo.cpp made the trick but I'm unsure if including the whole internal header is the best fix for this.

PS: I also had to add -limm32 to the compiler flag to make it link.

[ocornut]

I don't know which version you are looking at, but those ImStrdup were replaced with strdup a long time ago.

The opengl_example* Makefile already have -limm32 for mingw. Where did you have to add it?
You can define IMGUI_DISABLE_WIN32_DEFAULT_IME_FUNCS in imconfig.h to disable IME support and the need to link with it.

[Teybeo]

Sorry, i messed up my original message, now edited, the compiler error was about strdup not being declared (I copied the output after changing strdup to ImStrdup).

---

About imm32 I just copied the 3 sdl_opengl_example files and setup this CMakeLists.txt for building on Clion:

cmake_minimum_required(VERSION 3.4)
project(Imgui_demo)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

########### SDL paths ############

set(SDL_INCLUDE_DIR "D:/Dev/Lib/SDL2-2.0.3/i686-w64-mingw32/include/SDL2")
set(SDL_LIB_DIR "D:/Dev/Lib/SDL2-2.0.3/i686-w64-mingw32/lib")

find_library(SDL_LIBRARY
        NAMES SDL2
        HINTS ${SDL_LIB_DIR}
        NO_DEFAULT_PATH)

#################################

list(APPEND LIBRARIES ${SDL_LIBRARY})
list(APPEND LIBRARIES opengl32)
list(APPEND LIBRARIES imm32)

set(SOURCE_FILES main.cpp)
list(APPEND SOURCE_FILES imgui.cpp imgui.h)
list(APPEND SOURCE_FILES imgui_impl_sdl.cpp imgui_impl_sdl.h)
list(APPEND SOURCE_FILES imgui_demo.cpp)
list(APPEND SOURCE_FILES imgui_internal.h)
list(APPEND SOURCE_FILES imgui_draw.cpp)
list(APPEND SOURCE_FILES stb_rect_pack.h)
list(APPEND SOURCE_FILES stb_textedit.h)
list(APPEND SOURCE_FILES stb_truetype.h)

include_directories(${SDL_INCLUDE_DIR})
add_executable(Imgui_demo ${SOURCE_FILES})

target_link_libraries("Imgui_demo" ${LIBRARIES})

[ocornut]

Where is strdup declared with your compiler/system?

[Teybeo]

Ok I should have searched a bit more, when using the -std=c++11 flag, in string.h, the strdup and several other functions are ifdef'ed out under STRICT_ANSI

[ocornut]

What that's another annoyance caused by MinGW and modern compilers I suppose :/
Now switched to use a local function.

[ocornut]

About imm32: the docs are for Visual Studio but the Makefile for MinGW in OpenGL examples have the imm32 library. We could have an extra command-line example for MinGW if you want to submit a PR that cover various examples.

Ideally we have a better build system across all examples. cmake is just too ugly with the amount of temporary files it creates.

[ocornut]

FYI, leaving a note here for potential future readers stumbling here:

I have renamed those two defines that are usable (but very rarely used) in imconfig.h
IMGUI_DISABLE_WIN32_DEFAULT_CLIPBOARD_FUNCS became IMGUI_DISABLE_WIN32_DEFAULT_CLIPBOARD_FUNCTIONS.
IMGUI_DISABLE_WIN32_DEFAULT_IME_FUNCS became IMGUI_DISABLE_WIN32_DEFAULT_IME_FUNCTIONS.

Very few people will be affected and they will likely get a link error and therefore will notice.

The discussion in this thread pertain to using GCC/MinGW and both have those functions disabled already, so GCC/MinGW shouldn't be affected.

[mnba]

Ok I should have searched a bit more, when using the -std=c++11 flag, in string.h, the strdup and several other functions are ifdef'ed out under STRICT_ANSI

Not exactly STRICT_ANSI but STRICT_ANSI
The simplest solution I found for similar problem is ##undef it before including <pybind11/pybind11.h>, like this:

#undef  __STRICT_ANSI__
#include <pybind11/pybind11.h>