Skip libraries consisting of the empty string (#50899)

Co-authored-by: Gabriel Baraldi <baraldigabriel@gmail.com>
Co-authored-by: Jameson Nash <vtjnash@gmail.com>

Author: 3 people

src/jitlayers.cpp

@@ -1588,6 +1588,9 @@ struct JuliaOJIT::DLSymOptimizer {
                     assert(++++CI->use_begin() == CI->use_end());
                     void *addr;
                     if (auto GV = dyn_cast<GlobalVariable>(libarg)) {
+                        // Can happen if the library is the empty string, just give up when that happens
+                        if (isa<ConstantAggregateZero>(GV->getInitializer()))
+                            continue;
                         auto libname = cast<ConstantDataArray>(GV->getInitializer())->getAsCString();
                         addr = lookup(libname.data(), fname.data());
                     } else {

test/ccall.jl

@@ -1915,3 +1915,17 @@ end
     ctest_total_const() = Val{ctest_total(1 + 2im)}()
     Core.Compiler.return_type(ctest_total_const, Tuple{}) == Val{2 + 0im}
 end
+
+const libfrobozz = ""
+
+function somefunction_not_found()
+    ccall((:somefunction, libfrobozz), Cvoid, ())
+end
+
+@testset "library not found" begin
+    if Sys.islinux()
+        @test_throws "could not load symbol \"somefunction\"" somefunction_not_found()
+    else
+        @test_throws "could not load library \"\"" somefunction_not_found()
+    end
+end