Fix lookup of symbols at the same address with no size vs. size

This fixes a failing testcase on Fedora 30 x86_64 (regression Fedora 29->30):

PASS:
./bin/lldb ./lldb-test-build.noindex/functionalities/unwind/noreturn/TestNoreturnUnwind.test_dwarf/a.out -o 'settings set symbols.enable-external-lookup false' -o r -o bt -o quit
  * frame #0: 0x00007ffff7aa6e75 libc.so.6`__GI_raise + 325
    frame swiftlang#1: 0x00007ffff7a91895 libc.so.6`__GI_abort + 295
    frame swiftlang#2: 0x0000000000401140 a.out`func_c at main.c:12:2
    frame swiftlang#3: 0x000000000040113a a.out`func_b at main.c:18:2
    frame swiftlang#4: 0x0000000000401134 a.out`func_a at main.c:26:2
    frame swiftlang#5: 0x000000000040112e a.out`main(argc=<unavailable>, argv=<unavailable>) at main.c:32:2
    frame swiftlang#6: 0x00007ffff7a92f33 libc.so.6`__libc_start_main + 243
    frame swiftlang#7: 0x000000000040106e a.out`_start + 46

vs.

FAIL - unrecognized abort() function:
./bin/lldb ./lldb-test-build.noindex/functionalities/unwind/noreturn/TestNoreturnUnwind.test_dwarf/a.out -o 'settings set symbols.enable-external-lookup false' -o r -o bt -o quit
  * frame #0: 0x00007ffff7aa6e75 libc.so.6`.annobin_raise.c + 325
    frame swiftlang#1: 0x00007ffff7a91895 libc.so.6`.annobin_loadmsgcat.c_end.unlikely + 295
    frame swiftlang#2: 0x0000000000401140 a.out`func_c at main.c:12:2
    frame swiftlang#3: 0x000000000040113a a.out`func_b at main.c:18:2
    frame swiftlang#4: 0x0000000000401134 a.out`func_a at main.c:26:2
    frame swiftlang#5: 0x000000000040112e a.out`main(argc=<unavailable>, argv=<unavailable>) at main.c:32:2
    frame swiftlang#6: 0x00007ffff7a92f33 libc.so.6`.annobin_libc_start.c + 243
    frame swiftlang#7: 0x000000000040106e a.out`.annobin_init.c.hot + 46

The extra ELF symbols are there due to Annobin (I did not investigate why this problem happened specifically since F-30 and not since F-28).
It is due to:

Symbol table '.dynsym' contains 2361 entries:
Valu e          Size Type   Bind   Vis     Name
0000000000022769   5 FUNC   LOCAL  DEFAULT _nl_load_domain.cold
000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_abort.c.unlikely
...
000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_loadmsgcat.c_end.unlikely
...
000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_textdomain.c_end.unlikely
000000000002276e 548 FUNC   GLOBAL DEFAULT abort
000000000002276e 548 FUNC   GLOBAL DEFAULT abort@@GLIBC_2.2.5
000000000002276e 548 FUNC   LOCAL  DEFAULT __GI_abort
0000000000022992   0 NOTYPE LOCAL  HIDDEN  .annobin_abort.c_end.unlikely

Differential Revision: https://reviews.llvm.org/D63540

llvm-svn: 364773
(cherry picked from commit 3f594ed)

lldb/lit/SymbolFile/Inputs/sizeless-symbol.s

@@ -0,0 +1,8 @@
+        .text
+        .byte   0
+sizeless:
+sizeful:
+        .byte   0
+        .byte   0
+sizeend:
+        .size   sizeful, sizeend - sizeful

lldb/lit/SymbolFile/sizeless-symbol.test

@@ -0,0 +1,14 @@
+# Some targets do not have the .size directive.
+# RUN: %clang -target x86_64-unknown-unknown-elf %S/Inputs/sizeless-symbol.s -c -o %t.o
+# RUN: %lldb %t.o -s %s -o quit | FileCheck %s
+
+image lookup --address 1
+# CHECK: Summary: sizeless-symbol.test.tmp.o`sizeful
+image lookup --address 2
+# CHECK: Summary: sizeless-symbol.test.tmp.o`sizeful + 1
+image dump symtab
+# CHECK:     Index   UserID DSX Type            File Address/Value Load Address       Size               Flags      Name
+# CHECK-NEXT:------- ------ --- --------------- ------------------ ------------------ ------------------ ---------- ----------------------------------
+# CHECK-NEXT:[    0]      1     Code            0x0000000000000003                    0x0000000000000000 0x00000000 sizeend
+# CHECK-NEXT:[    1]      2     Code            0x0000000000000001                    0x0000000000000002 0x00000000 sizeful
+# CHECK-NEXT:[    2]      3     Code            0x0000000000000001                    0x0000000000000000 0x00000000 sizeless

lldb/source/Symbol/Symtab.cpp

@@ -896,8 +896,14 @@ void Symtab::InitAddressIndexes() {
       for (size_t i = 0; i < num_entries; i++) {
         FileRangeToIndexMap::Entry *entry =
             m_file_addr_to_index.GetMutableEntryAtIndex(i);
-        if (entry->GetByteSize() == 0) {
-          addr_t curr_base_addr = entry->GetRangeBase();
+        if (entry->GetByteSize() > 0)
+          continue;
+        addr_t curr_base_addr = entry->GetRangeBase();
+        // Symbols with non-zero size will show after zero-sized symbols on the
+        // same address. So do not set size of a non-last zero-sized symbol.
+        if (i == num_entries - 1 ||
+            m_file_addr_to_index.GetMutableEntryAtIndex(i + 1)
+                    ->GetRangeBase() != curr_base_addr) {
           const RangeVector<addr_t, addr_t>::Entry *containing_section =
               section_ranges.FindEntryThatContains(curr_base_addr);