https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91664
Bug ID: 91664
Summary: Undefined reference linker errors when static linking
archive with gcc target_clones function
multi-versioning
Product: gcc
Version: 8.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: element at elementsofsound dot org
Target Milestone: ---
Created attachment 46826
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46826&action=edit
Preprocessed file for fmv-test.c
Target: x86_64-linux-gnu
gcc version 8.3.0 (Ubuntu 8.3.0-6ubuntu1)
Creating a static library archive with publicly declared functions with
target_clones attribute, causes undefined reference errors to the function
clones when linking the archive into the final application.
I created a test build on github which illustrates this:
https://github.com/elementgreen/fmv-test
Also a stackoverflow question:
https://stackoverflow.com/questions/57798005/how-to-fix-undefined-reference-linker-errors-when-static-linking-archive-with-gc
This test build has 3 different make targets "works", "also_works", and
"borken". The first just builds the executable in one go with .c source files
and -o for the target executable. The second compiles each .c into .o object
files and then links them with gcc -o and the object files. The final make
target compiles each .c into .o files, then creates an archive with ar, and
then links the .a archive into the final executable with gcc -o. The first 2
targets work, the 3rd does not, with the errors:
gcc -c fmv-test.c
gcc -c main.c
ar cr fmv-test.a fmv-test.o main.o
gcc -o fmv-test-borken fmv-test.a
/usr/bin/ld: fmv-test.a(main.o): in function `fmv_test':
main.c:(.text.fmv_test.resolver[fmv_test.resolver]+0x1f): undefined reference
to `fmv_test.avx2.0'
/usr/bin/ld: main.c:(.text.fmv_test.resolver[fmv_test.resolver]+0x3b):
undefined reference to `fmv_test.avx.1'
/usr/bin/ld: main.c:(.text.fmv_test.resolver[fmv_test.resolver]+0x57):
undefined reference to `fmv_test.sse4_1.2'
/usr/bin/ld: main.c:(.text.fmv_test.resolver[fmv_test.resolver]+0x71):
undefined reference to `fmv_test.sse2.3'
/usr/bin/ld: main.c:(.text.fmv_test.resolver[fmv_test.resolver]+0x7a):
undefined reference to `fmv_test.default.4'
collect2: error: ld returned 1 exit status
