Enable --no-undefined-version by default

Recent lld version default to --no-undefined-version, which triggers
errors when building multiple libraries.  For ld.so on x86_64  it fails
with:

ld.lld: error: version script assignment of 'GLIBC_2.4' to symbol '__stack_chk_guard' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_PRIVATE' to symbol '__nptl_set_robust_list_avail' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_PRIVATE' to symbol '__pointer_chk_guard' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_PRIVATE' to symbol '_dl_starting_up' failed: symbol not defined

While for libc.so:

ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_clearerr' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_fgetc' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_fileno' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_freopen' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_fscanf' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_fseek' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_peekc_unlocked' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_stderr_' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_stdin_' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_stdout_' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_pclose' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_perror' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_rewind' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_scanf' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_setbuf' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_setlinebuf' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_wdefault_setbuf' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '_IO_wfile_setbuf' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '__ctype32_tolower' failed: symbol not defined
ld.lld: error: version script assignment of 'GLIBC_2.17' to symbol '__ctype32_toupper' failed: symbol not defined
ld.lld: error: too many errors emitted, stopping now (use --error-limit=0 to see all errors)

The version script is created with multiple missing symbols to simplify
the build for multiple ABIs, each of which may have different symbols.
For instance, __stack_chk_guard is defined by default. This avoids
requiring each ABI to add this symbol to its version script, depending
on the stack protector ABI it uses.

The libc.so warnings do show unused symbols being defined (like
_IO_clearerr), which might trigger potential errors depending on how
symbols are exported.  However, since we already have ABI checks for
missing and extra symbols, the linker's extra checks are not really
necessary.

The --no-undefined-version is the default for ld.bfd.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

diff --git a/Makerules b/Makerules
index 7714888cdc35aa6eb36bc85e5487155980a552e6..caa1e43faa45102a3b82d3a9a96e446332f3e565 100644 (file)
--- a/Makerules
+++ b/Makerules
@@ -508,7 +508,9 @@ ifeq ($(build-shared),yes)
 map-file = $(firstword $($(@F:.so=-map)) \
                       $(addprefix $(common-objpfx), \
                                   $(filter $(@F:.so=.map),$(version-maps))))
-load-map-file = $(map-file:%=-Wl,--version-script=%)
+# The map version is created with multiple symbols that might not be
+# exported depending of the ABI.
+load-map-file = $(map-file:%=-Wl,--version-script=%) -Wl,--undefined-version
 endif
 
 # Compiler arguments to use to link a shared object with libc and