[WIP] OpenMP 5.0: requires directive: workaround to fix libgomp IntelMIC plugin build

Fix-up for og10 commit c2e4a17adc0989f216c7fc3f93f150c66adba23a "OpenMP 5.0:
requires directive".

The GCC offloading target configurations don't build/use
'crtoffloadbegin.o'/'crtoffloadtable.o'/'crtoffloadend.o'
('libgcc/offloadstuff.c'), but the libgomp IntelMIC plugin still does link
against libgomp, and the latter unconditionally refers to
'__requires_mask_table', '__requires_mask_table_end':

    make[3]: Entering directory '[...]/build-gcc-offload-x86_64-intelmicemul-linux-gnu/x86_64-intelmicemul-linux-gnu/liboffloadmic/plugin'
    [...]/build-gcc-offload-x86_64-intelmicemul-linux-gnu/./gcc/xg++ [...] -loffloadmic_target -lcoi_device -lgomp -rdynamic ../ofldbegin.o offload_target_main.o ../ofldend.o -o offload_target_main
    ./../../libgomp/.libs/libgomp.so: undefined reference to `__requires_mask_table_end'
    ./../../libgomp/.libs/libgomp.so: undefined reference to `__requires_mask_table'
    collect2: error: ld returned 1 exit status
    Makefile:806: recipe for target 'offload_target_main' failed
    make[3]: *** [offload_target_main] Error 1

I have not researched what a proper fix would look like.

	libgomp/
	* target.c (__requires_mask_table, __requires_mask_table_end): Add
	'__attribute__((weak))'.

diff --git a/libgomp/ChangeLog.omp b/libgomp/ChangeLog.omp
index 0519191a93664281e5a843938f8554f264af56d8..db1d2bdac3ab7b5e51df6d7e8cbac8c9c782b453 100644 (file)
--- a/libgomp/ChangeLog.omp
+++ b/libgomp/ChangeLog.omp
@@ -1,3 +1,8 @@
+2021-03-25  Thomas Schwinge  <thomas@codesourcery.com>
+
+       * target.c (__requires_mask_table, __requires_mask_table_end): Add
+       '__attribute__((weak))'.
+
 2021-03-01  Kwok Cheung Yeung  <kcy@codesourcery.com>
 
        * testsuite/libgomp.c-c++-common/collapse-4.c: New.

diff --git a/libgomp/target.c b/libgomp/target.c
index af39d283608c1bb130e133afadda7c7b44a648ee..2633ab1e43f70e1f89435c05eb87be20d4c05f38 100644 (file)
--- a/libgomp/target.c
+++ b/libgomp/target.c
@@ -104,7 +104,9 @@ static unsigned int gomp_requires_mask;
 
 /* Start/end of .gnu.gomp.requires section of program, defined in
    crtoffloadbegin/end.o.  */
+__attribute__((weak))
 extern const unsigned int __requires_mask_table[];
+__attribute__((weak))
 extern const unsigned int __requires_mask_table_end[];
 
 /* Similar to gomp_realloc, but release register_lock before gomp_fatal.  */