[lld/mac] Don't crash on 32-bit output binaries when dead-stripping

[thakis]

Summary

Fixes PR50974.

[tschuett]

This is not the same as std::numeric_limits<Ptr>::max()?

[thakis]

In D105399#2857040, @tschuett wrote:

This is not the same as std::numeric_limits<Ptr>::max()?

Yes, it's the same.

[tschuett]

In D105399#2857058, @thakis wrote:

In D105399#2857040, @tschuett wrote:

This is not the same as std::numeric_limits<Ptr>::max()?

Yes, it's the same.

static_cast+ Macro feels hacky. numeric_limits is more descriptive.

[thakis]

In D105399#2857141, @tschuett wrote:

static_cast+ Macro feels hacky. numeric_limits is more descriptive.

I don't see any advantage to numeric_limits here.

[int3]

+1 for numeric_limits, it "constructs" the right value, whereas static_cast is "converting" the wrong value into the right one. but feel free to ignore :)

[thakis]

Fine, landed with numeric_limits.

lld/MachO/UnwindInfoSection.cpp

 // unwind info need explicit "no unwind info" unwind entries -- else the
 // unwinder would think they have the unwind info of the closest function
 // with unwind info right before in the image.
 template <class Ptr>
 static void addEntriesForFunctionsWithoutUnwindInfo(
     std::vector<CompactUnwindEntry<Ptr>> &cuVector) {
   DenseSet<Ptr> hasUnwindInfo;
   for (CompactUnwindEntry<Ptr> &cuEntry : cuVector)
-    if (cuEntry.functionAddress != UINT64_MAX)
+    if (cuEntry.functionAddress != static_cast<Ptr>(UINT64_MAX))
       hasUnwindInfo.insert(cuEntry.functionAddress);
 
   // Add explicit "has no unwind info" entries for all global and local symbols
   // without unwind info.
   auto markNoUnwindInfo = [&cuVector, &hasUnwindInfo](const Defined *d) {
     if (d->isLive() && d->isec && isCodeSection(d->isec)) {
       Ptr ptr = d->getVA();
       if (!hasUnwindInfo.count(ptr))

lld/test/MachO/compact-unwind.s

 # REQUIRES: x86, aarch64
 # RUN: rm -rf %t; split-file %s %t
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin19.0.0 %t/my-personality.s -o %t/x86_64-my-personality.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin19.0.0 %t/main.s -o %t/x86_64-main.o
 # RUN: %lld -arch x86_64 -pie -lSystem -lc++ %t/x86_64-my-personality.o %t/x86_64-main.o -o %t/x86_64-personality-first
 # RUN: llvm-objdump --macho --unwind-info --syms --indirect-symbols --rebase %t/x86_64-personality-first | FileCheck %s --check-prefixes=FIRST,CHECK -D#%x,BASE=0x100000000
-# RUN: %lld -arch x86_64 -pie -lSystem -lc++ %t/x86_64-main.o %t/x86_64-my-personality.o -o %t/x86_64-personality-second
+# RUN: %lld -dead_strip -arch x86_64 -pie -lSystem -lc++ %t/x86_64-main.o %t/x86_64-my-personality.o -o %t/x86_64-personality-second
 # RUN: llvm-objdump --macho --unwind-info --syms --indirect-symbols --rebase %t/x86_64-personality-second | FileCheck %s --check-prefixes=SECOND,CHECK -D#%x,BASE=0x100000000
 
 # RUN: llvm-mc -filetype=obj -triple=arm64-apple-darwin19.0.0 %t/my-personality.s -o %t/arm64-my-personality.o
 # RUN: llvm-mc -filetype=obj -triple=arm64-apple-darwin19.0.0 %t/main.s -o %t/arm64-main.o
 # RUN: %lld -arch arm64 -pie -lSystem -lc++ %t/arm64-my-personality.o %t/arm64-main.o -o %t/arm64-personality-first
 # RUN: llvm-objdump --macho --unwind-info --syms --indirect-symbols --rebase %t/arm64-personality-first | FileCheck %s --check-prefixes=FIRST,CHECK -D#%x,BASE=0x100000000
-# RUN: %lld -arch arm64 -pie -lSystem -lc++ %t/arm64-main.o %t/arm64-my-personality.o -o %t/arm64-personality-second
+# RUN: %lld -dead_strip -arch arm64 -pie -lSystem -lc++ %t/arm64-main.o %t/arm64-my-personality.o -o %t/arm64-personality-second
 # RUN: llvm-objdump --macho --unwind-info --syms --indirect-symbols --rebase %t/arm64-personality-second | FileCheck %s --check-prefixes=SECOND,CHECK -D#%x,BASE=0x100000000
 
 # RUN: llvm-mc -filetype=obj -triple=arm64_32-apple-watchos %t/my-personality.s -o %t/arm64-32-my-personality.o
 # RUN: llvm-mc -filetype=obj -triple=arm64_32-apple-watchos %t/main.s -o %t/arm64-32-main.o
 # RUN: %lld-watchos -pie -lSystem -lc++ %t/arm64-32-my-personality.o %t/arm64-32-main.o -o %t/arm64-32-personality-first
 # RUN: llvm-objdump --macho --unwind-info --syms --indirect-symbols --rebase %t/arm64-32-personality-first | FileCheck %s --check-prefixes=FIRST,CHECK -D#%x,BASE=0x4000
-# RUN: %lld-watchos -pie -lSystem -lc++ %t/arm64-32-main.o %t/arm64-32-my-personality.o -o %t/arm64-32-personality-second
+# RUN: %lld-watchos -dead_strip -pie -lSystem -lc++ %t/arm64-32-main.o %t/arm64-32-my-personality.o -o %t/arm64-32-personality-second
 # RUN: llvm-objdump --macho --unwind-info --syms --indirect-symbols --rebase %t/arm64-32-personality-second | FileCheck %s --check-prefixes=SECOND,CHECK -D#%x,BASE=0x4000
 
 # FIRST:      Indirect symbols for (__DATA_CONST,__got)
 # FIRST-NEXT: address                    index name
 # FIRST-DAG:  0x[[#%x,GXX_PERSONALITY:]] [[#]] ___gxx_personality_v0
 # FIRST-DAG:  0x[[#%x,MY_PERSONALITY:]]  LOCAL
 
 # SECOND:      Indirect symbols for (__DATA_CONST,__got)
_main:
   ret
   .cfi_endproc
 
 ## _quux has no unwind information.
 ## (In real life, it'd be part of a separate TU that was built with
 ## -fno-exceptions, while the previous and next TU might be Objective-C++
 ## which has unwind info for Objective-C).
 .p2align 2
+.no_dead_strip _quux
 _quux:
   ret
 
 .globl _abs
+.no_dead_strip _abs
 _abs = 4
 
 .p2align 2
+.no_dead_strip _baz
 _baz:
   .cfi_startproc
 ## This will generate a symbol relocation. Check that we reuse the personality
 ## referenced by the section relocation in my_personality.s.
   .cfi_personality 155, _my_personality
   .cfi_lsda 16, _exception1
   .cfi_def_cfa_offset 16
   ret
   .cfi_endproc
 
+.globl _stripped
+_stripped:
+  .cfi_startproc
+  .cfi_personality 155, ___gxx_personality_v0
+  .cfi_lsda 16, _exception1
+  .cfi_def_cfa_offset 16
+  ret
+  .cfi_endproc
+
 
 .section __TEXT,__gcc_except_tab
 _exception1:
   .space 1
+
+.subsections_via_symbols