meson, includedir, and current directory

Thu, 18 Jul 2024 13:16:28 -0000
pdo, debian, eng

Suppose you have a meson project like this:

meson.build:

project('example', 'cpp', version: '1.0', license : '…', default_options: ['warning_level=everything', 'cpp_std=c++17'])

subdir('example')

example/meson.build:

test_example = executable('example-test', ['main.cc'])

example/string.h:

/* This file intentionally left empty */

example/main.cc:

#include <cstring>

int main(int argc,const char* argv[])
{
    std::string foo("foo");
    return 0;
}

This builds fine with autotools and cmake, but not meson:

$ meson setup builddir
The Meson build system
Version: 1.0.1
Source dir: /home/enrico/dev/deb/wobble-repr
Build dir: /home/enrico/dev/deb/wobble-repr/builddir
Build type: native build
Project name: example
Project version: 1.0
C++ compiler for the host machine: ccache c++ (gcc 12.2.0 "c++ (Debian 12.2.0-14) 12.2.0")
C++ linker for the host machine: c++ ld.bfd 2.40
Host machine cpu family: x86_64
Host machine cpu: x86_64
Build targets in project: 1

Found ninja-1.11.1 at /usr/bin/ninja
$ ninja -C builddir
ninja: Entering directory `builddir'
[1/2] Compiling C++ object example/example-test.p/main.cc.o
FAILED: example/example-test.p/main.cc.o
ccache c++ -Iexample/example-test.p -Iexample -I../example -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -Wpedantic -Wcast-qual -Wconversion -Wfloat-equal -Wformat=2 -Winline -Wmissing-declarations -Wredundant-decls -Wshadow -Wundef -Wuninitialized -Wwrite-strings -Wdisabled-optimization -Wpacked -Wpadded -Wmultichar -Wswitch-default -Wswitch-enum -Wunused-macros -Wmissing-include-dirs -Wunsafe-loop-optimizations -Wstack-protector -Wstrict-overflow=5 -Warray-bounds=2 -Wlogical-op -Wstrict-aliasing=3 -Wvla -Wdouble-promotion -Wsuggest-attribute=const -Wsuggest-attribute=noreturn -Wsuggest-attribute=pure -Wtrampolines -Wvector-operation-performance -Wsuggest-attribute=format -Wdate-time -Wformat-signedness -Wnormalized=nfc -Wduplicated-cond -Wnull-dereference -Wshift-negative-value -Wshift-overflow=2 -Wunused-const-variable=2 -Walloca -Walloc-zero -Wformat-overflow=2 -Wformat-truncation=2 -Wstringop-overflow=3 -Wduplicated-branches -Wattribute-alias=2 -Wcast-align=strict -Wsuggest-attribute=cold -Wsuggest-attribute=malloc -Wanalyzer-too-complex -Warith-conversion -Wbidi-chars=ucn -Wopenacc-parallelism -Wtrivial-auto-var-init -Wctor-dtor-privacy -Weffc++ -Wnon-virtual-dtor -Wold-style-cast -Woverloaded-virtual -Wsign-promo -Wstrict-null-sentinel -Wnoexcept -Wzero-as-null-pointer-constant -Wabi-tag -Wuseless-cast -Wconditionally-supported -Wsuggest-final-methods -Wsuggest-final-types -Wsuggest-override -Wmultiple-inheritance -Wplacement-new=2 -Wvirtual-inheritance -Waligned-new=all -Wnoexcept-type -Wregister -Wcatch-value=3 -Wextra-semi -Wdeprecated-copy-dtor -Wredundant-move -Wcomma-subscript -Wmismatched-tags -Wredundant-tags -Wvolatile -Wdeprecated-enum-enum-conversion -Wdeprecated-enum-float-conversion -Winvalid-imported-macros -std=c++17 -O0 -g -MD -MQ example/example-test.p/main.cc.o -MF example/example-test.p/main.cc.o.d -o example/example-test.p/main.cc.o -c ../example/main.cc
In file included from ../example/main.cc:1:
/usr/include/c++/12/cstring:77:11: error: ‘memchr’ has not been declared in ‘::’
   77 |   using ::memchr;
      |           ^~~~~~
/usr/include/c++/12/cstring:78:11: error: ‘memcmp’ has not been declared in ‘::’
   78 |   using ::memcmp;
      |           ^~~~~~
/usr/include/c++/12/cstring:79:11: error: ‘memcpy’ has not been declared in ‘::’
   79 |   using ::memcpy;
      |           ^~~~~~
/usr/include/c++/12/cstring:80:11: error: ‘memmove’ has not been declared in ‘::’
   80 |   using ::memmove;
      |           ^~~~~~~
…

It turns out that meson adds the current directory to the include path by default:

Another thing to note is that include_directories adds both the source directory and corresponding build directory to include path, so you don't have to care.

It seems that I have to care after all.

Thankfully there is an implicit_include_directories setting that can turn this off if needed.

Its documentation is not as easy to find as I'd like (kudos to Kangie on IRC), and hopefully this blog post will make it easier for me to find it in the future.