# FYI : building Slicer with GCC 8.1

**URL:** <https://discourse.slicer.org/t/fyi-building-slicer-with-gcc-8-1/2830>\
**Category:** Development\
**Created:** [May 16, 2018, 8:06pm UTC](https://discourse.slicer.org/t/fyi-building-slicer-with-gcc-8-1/2830 "2018-05-16T20:06:48Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![chir.set](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/chir.set/32/66982_2.png) [@chir.set](https://discourse.slicer.org/u/chir.set)\
**Post date:** [May 16, 2018, 8:06pm UTC](https://discourse.slicer.org/t/fyi-building-slicer-with-gcc-8-1/2830/1 "2018-05-16T20:06:48Z")

</div>

Building Slicer with GCC 8.1.0 on Arch Linux succeeds with these three patches.

1. Use Python 2.7.15. Versions 2.7.{13,14} do not compile.

> ```
> diff --git a/CMake/CTestCustom.cmake.in b/CMake/CTestCustom.cmake.in
> index 96dde4b99..0b5f65ce7 100644
> --- a/CMake/CTestCustom.cmake.in
> +++ b/CMake/CTestCustom.cmake.in
> @@ -172,8 +172,8 @@ set(CTEST_CUSTOM_WARNING_EXCEPTION
> "warning: the use of .tmpnam_r. is dangerous, better use .mkstemp."
>  
> # Python - Windows
> - "(P|p)ython-2.7.13.(M|m)odules"
> - "(P|p)ython-2.7.13.PC"
> + "(P|p)ython-2.7.15.(M|m)odules"
> + "(P|p)ython-2.7.15.PC"
> "Include\\um\\winsock2.h.*warning C4005: 'INVALID_SOCKET': macro redefinition"
> # Python - Linux
> "Objects.unicodeobject.c.*warning:.*differ in signedness"
> diff --git a/SuperBuild/External_python.cmake b/SuperBuild/External_python.cmake
> index 98d92a5be..1b7fc5928 100644
> --- a/SuperBuild/External_python.cmake
> +++ b/SuperBuild/External_python.cmake
> @@ -53,11 +53,11 @@ if((NOT DEFINED PYTHON_INCLUDE_DIR
> OR NOT DEFINED PYTHON_LIBRARY
> OR NOT DEFINED PYTHON_EXECUTABLE) AND NOT ${CMAKE_PROJECT_NAME}_USE_SYSTEM_${proj})
>  
> - set(python_SOURCE_DIR "${CMAKE_BINARY_DIR}/Python-2.7.13")
> + set(python_SOURCE_DIR "${CMAKE_BINARY_DIR}/Python-2.7.15")
>  
> ExternalProject_Add(python-source
> - URL "https://www.python.org/ftp/python/2.7.13/Python-2.7.13.tgz"
> - URL_MD5 "17add4bf0ad0ec2f08e0cae6d205c700"
> + URL "https://www.python.org/ftp/python/2.7.15/Python-2.7.15.tgz"
> + URL_MD5 "045fb3440219a1f6923fefdabde63342"
> DOWNLOAD_DIR ${CMAKE_BINARY_DIR}
> SOURCE_DIR ${python_SOURCE_DIR}
> CONFIGURE_COMMAND ""
> 
> ```

1. Declare gcc 8 for ITKv4. The declared constants for GCC 7 do not seem to be used in the code (using grep to find out)

> ```
> diff --git a/Modules/ThirdParty/VNL/src/vxl/vcl/vcl_compiler.h b/Modules/ThirdParty/VNL/src/vxl/vcl/vcl_compiler.h
> index 3f1bb01144..db3e7a6091 100644
> --- a/Modules/ThirdParty/VNL/src/vxl/vcl/vcl_compiler.h
> +++ b/Modules/ThirdParty/VNL/src/vxl/vcl/vcl_compiler.h
> @@ -75,7 +75,7 @@
> # else
> # define VCL_GCC_60
> # endif
> -# elif ( __GNUC__ ==7)
> +# elif ( __GNUC__ ==7) 
> # define VCL_GCC_7
> # if ( __GNUC_MINOR__ > 2 )
> # define VCL_GCC_73
> @@ -86,6 +86,13 @@
> # else
> # define VCL_GCC_70
> # endif
> +# elif ( __GNUC__ ==8)
> +# define VCL_GCC_8
> +# if ( __GNUC_MINOR__ > 0 )
> +# define VCL_GCC_81
> +# else
> +# define VCL_GCC_80
> +# endif
> # else
> # error "Dunno about this gcc"
> # endif
> 
> ```

1. Avoid this error while compiling VTKv9 : H5detect.c:1363:1: error: attributes should be specified before the declarator in a function definition

> ```
> diff --git a/ThirdParty/hdf5/vtkhdf5/src/H5detect.c b/ThirdParty/hdf5/vtkhdf5/src/H5detect.c
> index b2c958e5c4..bb32265b18 100644
> --- a/ThirdParty/hdf5/vtkhdf5/src/H5detect.c
> +++ b/ThirdParty/hdf5/vtkhdf5/src/H5detect.c
> @@ -1361,7 +1361,7 @@ bit.\n";
> *-------------------------------------------------------------------------
> */
> static void
> -detect_C89_integers(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_C89_integers(void) 
> {
> DETECT_BYTE(signed char, SCHAR, d_g[nd_g]); nd_g++;
> DETECT_BYTE(unsigned char, UCHAR, d_g[nd_g]); nd_g++;
> @@ -1389,7 +1389,7 @@ detect_C89_integers(void) HDF_NO_UBSAN
> *-------------------------------------------------------------------------
> */
> static void
> -detect_C89_floats(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_C89_floats(void)
> {
> DETECT_F(float, FLOAT, d_g[nd_g]); nd_g++;
> DETECT_F(double, DOUBLE, d_g[nd_g]); nd_g++;
> @@ -1411,7 +1411,7 @@ detect_C89_floats(void) HDF_NO_UBSAN
> *-------------------------------------------------------------------------
> */
> static void
> -detect_C99_integers8(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_C99_integers8(void) 
> {
> #if H5_SIZEOF_INT8_T>0
> #if H5_SIZEOF_INT8_T==1
> @@ -1473,7 +1473,7 @@ detect_C99_integers8(void) HDF_NO_UBSAN
> *-------------------------------------------------------------------------
> */
> static void
> -detect_C99_integers16(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_C99_integers16(void) 
> {
> #if H5_SIZEOF_INT16_T>0
> DETECT_I(int16_t, INT16, d_g[nd_g]); nd_g++;
> @@ -1511,7 +1511,7 @@ detect_C99_integers16(void) HDF_NO_UBSAN
> *-------------------------------------------------------------------------
> */
> static void
> -detect_C99_integers32(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_C99_integers32(void) 
> {
> #if H5_SIZEOF_INT32_T>0
> DETECT_I(int32_t, INT32, d_g[nd_g]); nd_g++;
> @@ -1549,7 +1549,7 @@ detect_C99_integers32(void) HDF_NO_UBSAN
> *-------------------------------------------------------------------------
> */
> static void
> -detect_C99_integers64(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_C99_integers64(void) 
> {
> #if H5_SIZEOF_INT64_T>0
> DETECT_I(int64_t, INT64, d_g[nd_g]); nd_g++;
> @@ -1600,7 +1600,7 @@ detect_C99_integers64(void) HDF_NO_UBSAN
> *-------------------------------------------------------------------------
> */
> static void
> -detect_C99_integers(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_C99_integers(void) 
> {
> /* break it down to more subroutines so that each module subroutine */
> /* is smaller and takes less time to compile with optimization on. */
> @@ -1626,7 +1626,7 @@ detect_C99_integers(void) HDF_NO_UBSAN
> *-------------------------------------------------------------------------
> */
> static void
> -detect_C99_floats(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_C99_floats(void) 
> {
> #if H5_SIZEOF_DOUBLE == H5_SIZEOF_LONG_DOUBLE
> /*
> @@ -1657,7 +1657,7 @@ detect_C99_floats(void) HDF_NO_UBSAN
> *-------------------------------------------------------------------------
> */
> static void
> -detect_alignments(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN detect_alignments(void) 
> {
> /* Detect structure alignment for pointers, hvl_t, hobj_ref_t, hdset_reg_ref_t */
> DETECT_M(void *, POINTER, m_g[na_g]); na_g++;
> @@ -1745,7 +1745,7 @@ static int verify_signal_handlers(int signum, void (*handler)(int))
> *-------------------------------------------------------------------------
> */
> int
> -main(void) HDF_NO_UBSAN
> +HDF_NO_UBSAN main(void) 
> {
>  
> #if defined(H5_HAVE_SETSYSINFO) && defined(SSI_NVPAIRS)
> 
> ```

Just for informational purposes.

---

<div class="post-metadata">

**Author:** ![phcerdan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/phcerdan/32/1559_2.png) [@phcerdan](https://discourse.slicer.org/u/phcerdan)\
**Post date:** [May 16, 2018, 8:54pm UTC](https://discourse.slicer.org/t/fyi-building-slicer-with-gcc-8-1/2830/2 "2018-05-16T20:54:48Z")

</div>

This is great @chir.set, thanks for reporting it. I hitted the same issues this morning using arch 😃

> [@chir.set](#):
>
> 1. Use Python 2.7.15. Versions 2.7.{13,14} do not compile.

@jcfr might have a say on this one. Thanks for the suggested solution!

> [@chir.set](#):
>
> Avoid this error while compiling VTKv9 : H5detect.c:1363:1: error: attributes should be specified before the declarator in a function definition

VXL has been fixed already (and merged) : [COMP: Add gcc8 support to vcl\_compiler. · vxl/vxl@2662860 · GitHub](https://github.com/vxl/vxl/commit/2662860491ff44a16e01581a6b3727d53997fee8)

And the update for ITK to use the updated VXL is in review: [http://review.source.kitware.com/#/c/23437/1](http://review.source.kitware.com/#/c/23437/1)

> [@chir.set](#):
>
> 1. Avoid this error while compiling VTKv9 : H5detect.c:1363:1: error: attributes should be specified before the declarator in a function definition

Reported to VTK with your patch suggestion: [Errors in H5detect (#17316) · Issues · VTK / VTK · GitLab](https://gitlab.kitware.com/vtk/vtk/issues/17316)

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**Author:** ![jcfr](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jcfr/32/17825_2.png) [@jcfr](https://discourse.slicer.org/u/jcfr)\
**Post date:** [May 16, 2018, 9:08pm UTC](https://discourse.slicer.org/t/fyi-building-slicer-with-gcc-8-1/2830/3 "2018-05-16T21:08:15Z")

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@chir.set @phcerdan Thanks for your help with this.

> Python 2.7.13 → Python 2.7.15

Makes sense. We will update the version used in Slicer.

> error while compiling VTKv9

I added a comment [Errors in H5detect (#17316) · Issues · VTK / VTK · GitLab](https://gitlab.kitware.com/vtk/vtk/issues/17316) referencing the HDF5 upstream fix that could be backported to the VTK fork of hdf5

---

<div class="post-metadata">

**Author:** ![phcerdan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/phcerdan/32/1559_2.png) [@phcerdan](https://discourse.slicer.org/u/phcerdan)\
**Post date:** [October 25, 2018, 12:09am UTC](https://discourse.slicer.org/t/fyi-building-slicer-with-gcc-8-1/2830/4 "2018-10-25T00:09:45Z")

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For completion in this thread, I have been using `USE_SYSTEM_python:BOOL=ON` in Archlinux to overcome the following bug in [python-cmake-buildsystem](https://github.com/python-cmake-buildsystem/python-cmake-buildsystem/issues/224) about missing the header `rpc.h`. This happens to me with `python-2.7.15` too.