diff options
| -rw-r--r-- | Makefile | 1 | ||||
| -rw-r--r-- | compiler-tricks/not-constant.c | 2 | ||||
| -rw-r--r-- | config.mak.dev | 1 | ||||
| -rw-r--r-- | git-compat-util.h | 9 | ||||
| -rw-r--r-- | meson.build | 2 | ||||
| -rw-r--r-- | run-command.c | 8 |
6 files changed, 22 insertions, 1 deletions
@@ -995,6 +995,7 @@ LIB_OBJS += common-init.o LIB_OBJS += compat/nonblock.o LIB_OBJS += compat/obstack.o LIB_OBJS += compat/terminal.o +LIB_OBJS += compiler-tricks/not-constant.o LIB_OBJS += config.o LIB_OBJS += connect.o LIB_OBJS += connected.o diff --git a/compiler-tricks/not-constant.c b/compiler-tricks/not-constant.c new file mode 100644 index 0000000000..1da3ffc2f5 --- /dev/null +++ b/compiler-tricks/not-constant.c @@ -0,0 +1,2 @@ +#include <git-compat-util.h> +int false_but_the_compiler_does_not_know_it_; diff --git a/config.mak.dev b/config.mak.dev index 0fd8cc4d35..95b7bc46ae 100644 --- a/config.mak.dev +++ b/config.mak.dev @@ -39,6 +39,7 @@ DEVELOPER_CFLAGS += -Wunused DEVELOPER_CFLAGS += -Wvla DEVELOPER_CFLAGS += -Wwrite-strings DEVELOPER_CFLAGS += -fno-common +DEVELOPER_CFLAGS += -Wunreachable-code ifneq ($(filter clang4,$(COMPILER_FEATURES)),) DEVELOPER_CFLAGS += -Wtautological-constant-out-of-range-compare diff --git a/git-compat-util.h b/git-compat-util.h index e123288e8f..cf733b38ac 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -1583,4 +1583,13 @@ static inline void *container_of_or_null_offset(void *ptr, size_t offset) ((uintptr_t)&(ptr)->member - (uintptr_t)(ptr)) #endif /* !__GNUC__ */ +/* + * Prevent an overly clever compiler from optimizing an expression + * out, triggering a false positive when building with the + * -Wunreachable-code option. false_but_the_compiler_does_not_know_it_ + * is defined in a compilation unit separate from where the macro is + * used, initialized to 0, and never modified. + */ +#define NOT_CONSTANT(expr) ((expr) || false_but_the_compiler_does_not_know_it_) +extern int false_but_the_compiler_does_not_know_it_; #endif diff --git a/meson.build b/meson.build index 0902e12189..33d92c066c 100644 --- a/meson.build +++ b/meson.build @@ -264,6 +264,7 @@ libgit_sources = [ 'compat/nonblock.c', 'compat/obstack.c', 'compat/terminal.c', + 'compiler-tricks/not-constant.c', 'config.c', 'connect.c', 'connected.c', @@ -719,6 +720,7 @@ if get_option('warning_level') in ['2','3', 'everything'] and compiler.get_argum '-Woverflow', '-Wpointer-arith', '-Wstrict-prototypes', + '-Wunreachable-code', '-Wunused', '-Wvla', '-Wwrite-strings', diff --git a/run-command.c b/run-command.c index 402138b8b5..8833b23367 100644 --- a/run-command.c +++ b/run-command.c @@ -515,7 +515,13 @@ static void atfork_prepare(struct atfork_state *as) { sigset_t all; - if (sigfillset(&all)) + /* + * POSIX says sigfillset() can fail, but an overly clever + * compiler can see through the header files and decide + * it cannot fail on a particular platform it is compiling for, + * triggering -Wunreachable-code false positive. + */ + if (NOT_CONSTANT(sigfillset(&all))) die_errno("sigfillset"); #ifdef NO_PTHREADS if (sigprocmask(SIG_SETMASK, &all, &as->old)) |