add meson stuff

content/post/cmake-meson-compcert.md

@@ -0,0 +1,39 @@
+---
+title: "CMake & Meson & CompCert"
+date: 2020-06-07T16:13:00+02:00
+draft: false
+categories: [c, development]
+tags: [c]
+url: /posts/cmake-meson-compcert/
+author: "Christoph Cullmann"
+---
+
+I tried to compile the [Picolibc](https://github.com/keith-packard/picolibc) that uses the [Meson build system](https://mesonbuild.com/) with [CompCert](http://compcert.inria.fr/).
+
+The CompCert install I tried uses the GNU/GCC toolchain for preprocessing and linking.
+That makes the compiler relatively compatible to a GCC, beside that not all command line options are supported.
+
+I was used to [CMake](https://www.cmake.org) projects and there it is normally enough to just set CC=ccomp and you are ready and set (at least if you use the GNU/GCC toolchain).
+As long as you don't use special flags in your project, that will just work.
+
+The Picolibc was the first Meson based project I encountered.
+
+There setting CC to ccomp just leads to
+
+{{< highlight bash >}}
+ meson.build:1:0: ERROR: Unknown compiler(s): [['ccomp']]
+{{< / highlight >}}
+
+I did assume that the project won't compile & link without adjustments, as CompCert doesn't support the full range of command line options like GCC as mentioned above nor the full GNU extensions for C.
+But that it directly ends at the compiler initialization in the build system itself was astonishing.
+
+I searched a bit in the internet and it seems, if I really want to get this working, I actually need to patch Meson itself :/
+(see how to add a new compiler [here](https://github.com/mesonbuild/meson/commit/74602928100394f6129e064f8e0bfe6c9e08c9d2#diff-1eaa302b42bbbba32f1c6d474d08397e)
+
+At least I found no other solution, actually, I found no real solution for the above error message at all and the code looks like you need to manually add compilers anyways.
+
+Given I want to spend work on getting the C library to compile and not fix a build system, it seems easier to go with the [newlib](https://github.com/mirror/newlib-cygwin) that uses the old autotools,
+at least for them the compile starts at all with my CC environment variable and you get to places of interest to fix.
+
+This means for my use case, with a non-standard compiler, I can not see how Meson is an improvement over other existing stuff like CMake or even autotools.
+But perhaps this area will improve in the future.