Fix bug with zero length target sections

Created using spr 1.3.6-beta.1

Author: pcc

lld/ELF/Arch/X86_64.cpp

@@ -437,7 +437,7 @@ void X86_64::relaxCFIJumpTables() const {
           ++rnext;
         if (rcur + 1 == rnext) {
           InputSection *target = getMovableSection(*rcur);
-          if (target && target->size <= sec->entsize &&
+          if (target && target->size != 0 && target->size <= sec->entsize &&
               target->addralign <= sec->entsize &&
               target->getParent() == targetOutputSec) {
             // Okay, we found a small enough section. Move it into the jump

lld/test/ELF/x86_64-relax-jump-tables.s lld/test/ELF/x86-64-relax-jump-tables.slld/test/ELF/x86_64-relax-jump-tables.s renamed to lld/test/ELF/x86-64-relax-jump-tables.s

@@ -120,12 +120,19 @@ f14:
 jmp f14.cfi
 .balign 8, 0xcc
 
+// Empty target section.
 // CHECK: <f15>:
 // CHECK-NEXT: jmp {{.*}} <f15.cfi>
 f15:
 jmp f15.cfi
 .balign 8, 0xcc
 
+// CHECK: <f16>:
+// CHECK-NEXT: jmp {{.*}} <f16.cfi>
+f16:
+jmp f16.cfi
+.balign 8, 0xcc
+
 // CHECK: <f1>:
 // CHECK-NEXT: <f1.cfi>:
 // CHECK-NEXT: retq $0x1
@@ -202,9 +209,12 @@ f14.cfi:
 ret $14
 
 .section .text.f15,"ax",@progbits
-.balign 64
 f15.cfi:
-ret $15
+
+.section .text.f16,"ax",@progbits
+.balign 64
+f16.cfi:
+ret $16
 .zero 16
 
 // CHECK: <.iplt>: