Compiler warnings

[sevu]

I guess I'm the only one who gets them … (1.15)

In function 'createstrobj',
inlined from 'luaS_createlngstrobj' at src/lua/lstring.cpp:148:29,
inlined from 'luaS_newlstr' at src/lua/lstring.cpp:206:30:
src/lua/lstring.cpp:142:17: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
142 |   getstr(ts)[l] = '\0';  /* ending 0 */
|                 ^
src/lua/lstring.cpp: In function 'luaS_newlstr':
src/lua/lstate.h:213: note: at offset 0 to object 'ts' with size 24 declared here
213 |   struct TString ts;
|
In function 'createstrobj',
inlined from 'luaS_createlngstrobj' at src/lua/lstring.cpp:148:29,
inlined from 'luaS_newlstr' at src/lua/lstring.cpp:206:30,
inlined from 'luaX_newstring' at src/lua/llex.cpp:130:29:
src/lua/lstring.cpp:142:17: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
142 |   getstr(ts)[l] = '\0';  /* ending 0 */
|                 ^
src/lua/llex.cpp: In function 'luaX_newstring':
src/lua/lstate.h:213: note: at offset 0 to object 'ts' with size 24 declared here
213 |   struct TString ts;
|
In function 'createstrobj',
inlined from 'luaS_createlngstrobj' at src/lua/lstring.cpp:148:29,
inlined from 'luaS_newlstr' at src/lua/lstring.cpp:206:30,
inlined from 'pushstr' at src/lua/lobject.cpp:391:3,
inlined from 'luaO_pushvfstring' at src/lua/lobject.cpp:405:12:
src/lua/lstring.cpp:142:17: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
142 |   getstr(ts)[l] = '\0';  /* ending 0 */
|                 ^
src/lua/lobject.cpp: In function 'luaO_pushvfstring':
src/lua/lstate.h:213: note: at offset 0 to object 'ts' with size 24 declared here
213 |   struct TString ts;
|

[Pentarctagon]

How are you building wesnoth? A fix for scons at least was added in d643edc

[irydacea]

It would help a lot to know more about the particular compiler version and platform as well.

[sevu]

I built from a branch without this commit yet. But I tested again with today's master (63b16ad), and it's the same, with the above remaining unchanged.

As compiler I used gcc 10.2.
build system was scons,
build host was Archlinux,
library versions … I think are not relevant, as it's about out packaged Lua and the compiler.

Fun fact: GCC doesn't print inlined from … lines when using the German localisation.

[Pentarctagon]

I guess this will have to wait until GCC 10 is more widely available. I can't test this myself yet, and the commit linked above seems to have fixed this for loonycyborg.

[soliton-]

Are you saying you get stringop-overflow warnings even though it is turned off?

[sevu]

It happens during linking, scons doesn't pass -Wno-stringop-overflow to the linker.

When executing the linking command myself with the option it's turned off.

[soliton-]

Can you show the command? Really seems weird that option would do anything when linking.

[sevu]

g++ -o wesnoth -pthread -fstack-protector-strong -fPIE -pie -Wl,-z,relro,-z,now -O3 -march=native -flto=4 -fuse-ld=gold -Wl,-O1,--sort-common,--as-needed -Wl,--whole-archive build/release/libwesnoth-widgets.a -Wl,--no-whole-archive build/release/wesnoth.o build/release/libwesnoth-client.a build/release/liblua.a build/release/libwesnoth-core.a build/release/libwesnoth-game.a build/release/libwesnoth-sdl.a build/release/libwesnoth-client.a -lboost_regex -lboost_filesystem -lboost_locale -lboost_thread -lboost_system -lboost_random -lboost_program_options -lboost_iostreams -lm -lpthread -licudata -licui18n -licuuc -lcrypto -lSDL2 -lSDL2_ttf -lSDL2_mixer -lSDL2_image -lvorbisfile -lpangocairo-1.0 -lpango-1.0 -lgobject-2.0 -lglib-2.0-lharfbuzz -lcairo -lfontconfig -lfreetype -lX11 -ldbus-1 -lfribidi -lhistory

I specified a few custom options:
extra_flags_config = '-pipe -Wno-stringop-overflow'
extra_flags_release = '-fno-plt -Wl,-O1,--sort-common,--as-needed'
enable_lto = True
arch = 'native'

I see in the command the -Wl,-O1,--sort-common,--as-needed was taken from extra_flags_release, but -fno-plt not, so scons filters them out somewhere.

[Pentarctagon]

Does it happen if you build without LTO enabled?

[sevu]

No, only with LTO.

[Pentarctagon]

I'm not sure if it's something really fixable by us then, since it feels like it would be incorrect to add that warning suppression to the entire linking step when we only want it to apply to particular source files.