Each matlab release contains within it an entire set of compiled open-source libraries and binaries for each of the platforms it supports: Linux, OSX, and Win64.
| Directory | Files |
|---|---|
| /bin/ | |
| /bin// | Executables and shared |
It uses the various mechanisms available on those platforms to attempt to force dynamically loaded MEX modules to use those built-in libraries to varying degrees of success. For simple libraries that rely mainly on the Matlab C API, correctly linking a
MEX module is relatively straightforward, and there is even a built-in Matlab command mex that wraps calls to GCC.
However, complex applications with external dependencies run into several problems
On Linux, MEX modules have .mexa64 suffixes, but they are nothing more than renamed shared library (.so) files in the ELF format.
When the MEX function is called, the main Matlab executable $MATLAB_ROOT/bin/glnxa64/MATLAB uses the dlopen() function to dynamically load the MEX file and looks for a symbol with the name mexFunction to call. Basically any shared library with a mexFunction symbol and the right file extension could potentially work as a Matlab MEX module, but that's the easy part.
The difficulties begin as soon as a MEX module has it's own shared library dependencies.
The Linux dynamic library loading dependency resolution procedure depends on the executable making the dlopen calls. In this case, readelf -d bin/glnxa64/MATLAB has the following relevant lines:
...
0x0000000000000001 (NEEDED) Shared library: [libmwi18n.so]
0x0000000000000001 (NEEDED) Shared library: [libmwmvm.so]
0x0000000000000001 (NEEDED) Shared library: [libmwservices.so]
0x0000000000000001 (NEEDED) Shared library: [libmwboost_system.so.1.65.1]
0x0000000000000001 (NEEDED) Shared library: [libmwcpp11compat.so]
0x0000000000000001 (NEEDED) Shared library: [libpthread.so.0]
0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000f (RPATH) Library rpath: [$ORIGIN:$ORIGIN/../../sys/os/glnxa64]
...The last line indicated that the MATLAB executable sets the DT_RPATH attribute for the runtime path. This has important implications for MEX librararies as unlike the similar DT_RUNPATH attribute, the DT_RPATH has a recursive effect on the dependency resolution order. This is not at all clear from the dlopen() man page, which
On Linux when a library is dynamically loaded the following proceedure is followed:
- If the executable calling program (Matlab)
On Linux the matlab executable is $MATLAB_ROOT/bin/glnxa64/MATLAB.
Unless loading object has RUNPATH: RPATH of the loading object, then the RPATH of its loader (unless it has a RUNPATH), ..., until the end of the chain, which is either the executable or an object loaded by dlopen Unless executable has RUNPATH: RPATH of the executable LD_LIBRARY_PATH RUNPATH of the loading object ld.so.cache default dirs
The version of GCC cannot be newer than that used by the target Matlab release. In the case of C++ this restriction arises from the fact that libstdc++.so is backwards- but not forwards-compatible, other potential incompatibilities can be found in the GCC ABI Policy. This means that any MEX module built with GCC with a newer version of GLIBCXX or CXXABI than those used by Matlab will crash and burn.
This becomes a problem because Matlab's official GCC version support typically uses GCC versions that are 3-5 years behind the current stable versions used in many Linux distributions.
| Matlab Release | Matlab Ver. | GCC Ver. | GLIBCXX | CXXABI | Compatible GCC | C++11/14/17 |
|---|---|---|---|---|---|---|
| R2012b | 8.0 | 4.4.x | 3.4.13 | 1.3.3 | 4.4.7 | Very-Limited C++11 |
| R2013a | 8.1 | 4.4.x | 3.4.13 | 1.3.3 | 4.4.7 | Very-Limited C++11 |
| R2013b | 8.2 | 4.7.x | 3.4.17 | 1.3.3 | 4.7.4 | Limited C++11 |
| R2014a | 8.3 | 4.7.x | 3.4.17 | 1.3.3 | 4.7.4 | Limited C++11 |
| R2014b | 8.4 | 4.7.x | 3.4.17 | 1.3.3 | 4.7.4 | Limited C++11 |
| R2015a | 8.5 | 4.7.x | 3.4.17 | 1.3.3 | 4.7.4 | Limited C++11 |
| R2015b | 8.6 | 4.7.x | 3.4.17 | 1.3.3 | 4.7.4 | Limited C++11 |
| R2016a | 9.0 | 4.7.x | 3.4.17 | 1.3.3 | 4.7.4 | Limited C++11 |
| R2016b | 9.1 | 4.9.x | 3.4.20 | 1.3.8 | 4.9.4 | Full C++11 Limited C++14 |
| R2017a | 9.2 | 4.9.x | 3.4.20 | 1.3.8 | 4.9.4 | Full C++11 Limited C++14 |
| R2017b | 9.3 | 4.9.x | 3.4.20 | 1.3.8 | 4.9.4 | Full C++11 Limited C++14 |
| R2018a | 9.4 | 6.3.x | 3.4.22 | 1.3.10 | 6.5.0 | Full C++14 Limited C++17 |
| R2018b | 9.5 | 6.3.x | 3.4.22 | 1.3.10 | 6.5.0 | Full C++14 Limited C++17 |
| R2019a | 9.6 | 6.3.x | 3.4.22 | 1.3.10 | 6.5.0 | Full C++14 Limited C++17 |