Build fails with LTO

[eli-schwartz]

I tried to build with the following *FLAGS to optimize the build: -flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing

Note the -Werror=* flags are used to help detect cases where the compiler tries to optimize by assuming UB cannot exist in the source code -- if it does exist, ordinarily the code would be miscompiled, and this says to make the miscompilation a fatal error.

I got this error:

x86_64-pc-linux-gnu-gcc -march=native -fstack-protector-all -O2 -pipe -fdiagnostics-color=always -frecord-gcc-switches -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 -fstack-clash-protection -flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing  -Wformat -Werror=format-security -Werror=implicit-function-declaration -Werror=implicit-int -Werror=int-conversion -Werror=incompatible-pointer-types -Wall -Wextra         -DPACKAGE_NAME=\"rdesktop\" -DPACKAGE_TARNAME=\"rdesktop\" -DPACKAGE_VERSION=\"1.9.0\" -DPACKAGE_STRING=\"rdesktop\ 1.9.0\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DHAVE_STDIO_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_STRINGS_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_UNISTD_H=1 -DSTDC_HEADERS=1 -DL_ENDIAN=1 -DHAVE_SYS_SELECT_H=1 -DHAVE_LOCALE_H=1 -DHAVE_LANGINFO_H=1 -DHAVE_SYSEXITS_H=1 -DHAVE_XCURSOR=1 -DEGD_SOCKET=\"/var/run/egd-pool\" -DHAVE_LIBSAMPLERATE=1 -DWITH_RDPSND=1 -DRDPSND_ALSA=1 -DHAVE_DIRENT_H=1 -DHAVE_DIRFD=1 -DHAVE_DECL_DIRFD=1 -DHAVE_ICONV_H=1 -DHAVE_ICONV=1 -DICONV_CONST= -DHAVE_SYS_VFS_H=1 -DHAVE_SYS_STATVFS_H=1 -DHAVE_SYS_STATFS_H=1 -DHAVE_SYS_PARAM_H=1 -DHAVE_SYS_MOUNT_H=1 -DSTAT_STATVFS=1 -DHAVE_STRUCT_STATVFS_F_NAMEMAX=1 -DHAVE_STRUCT_STATFS_F_NAMELEN=1 -DHAVE_MNTENT_H=1 -DHAVE_SETMNTENT=1 -DIPv6=1 -DKEYMAP_PATH=\"/usr/share/rdesktop/keymaps/\" -o rdesktop rdesktop.o xwin.o xkeymap.o ewmhints.o xclip.o cliprdr.o ctrl.o rdpsnd.o rdpsnd_dsp.o rdpsnd_alsa.o tcp.o asn.o iso.o mcs.o secure.o licence.o rdp.o orders.o bitmap.o cache.o rdp5.o channels.o rdpdr.o serial.o printer.o disk.o parallel.o printercache.o mppc.o pstcache.o lspci.o seamless.o ssl.o utils.o stream.o dvc.o rdpedisp.o   -Wl,-O1 -Wl,--as-needed -flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing -Wl,--defsym=__gentoo_check_ldflags__=0 -lgmp  -lXcursor -ltasn1 -lnettle -lhogweed -lgnutls -lsamplerate -lasound    -lX11
xkeymap.c:40:13: error: type of ‘g_keymapname’ does not match original declaration [-Werror=lto-type-mismatch]
   40 | extern char g_keymapname[16];
      |             ^
rdesktop.c:66:6: note: array types have different bounds
   66 | char g_keymapname[PATH_MAX] = "";
      |      ^
rdesktop.c:66:6: note: ‘g_keymapname’ was previously declared here
lto1: some warnings being treated as errors
lto-wrapper: fatal error: x86_64-pc-linux-gnu-gcc returned 1 exit status
compilation terminated.
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
make: *** [Makefile:35: rdesktop] Error 1

Downstream report: https://bugs.gentoo.org/861824
Full build log: build.log