This patch updates m4/compiler-warnings.m4 as follows to make it more
compatible with clang:
* clang doesn't support -Wunused-but-set-variable, which can be replaced
with -Wunused-variable as the latter covers unused variables with or
without an assigned value and is supported by gcc and clang.
* -Wno-unused-function is added to let clang ignore unused functions that
are auto-generated.
By default the build used -Wno-unused-but-set-variable but that's
clearly not what we want. Fix those problems.
When using clang, the compiler doesn't error on unknown compile
options, so let's add -Werror to the checking too.
CC='clang'
configure:3408: checking for gcc
configure:3435: result: clang
...
configure:17644: checking whether gcc understands -Wno-unused-but-set-variable
configure:17657: clang -c -Wall -std=gnu89 -g -O2 -Wmissing-declarations -Wmissing-prototypes -Wdeclaration-after-statement -Wstrict-prototypes -Wno-unused-parameter -Wno-sign-compare -Wno-deprecated-declarations -Wno-unused-but-set-variable conftest.c >&5
warning: unknown warning option '-Wno-unused-but-set-variable'; did you mean '-Wno-unused-const-variable'? [-Wunknown-warning-option]
1 warning generated.
configure:17657: $? = 0
configure:17666: result: yes
Reported-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
It's annoying for distributors to build with -Werror, since it means
that compiler upgrades can break the build. Let's let them disable it,
but keep it enabled by default.
We now don't break the strict aliasing rules.
Also, having a compiler flag that disables a warning among the flags that are
meant to add extra sanity checking is not correct either:
--enable-extra-warnings=no would generate a bad aliasin warning while
the --enable-extra-warnings=yes would not.
GValueArray is deprecated since GLib 2.31.14, but we need to use it for
dbus-glib based code.
We should re-enable deprecation warnings once we switch to GDBus.
