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[SR-6046] DWARF generated by llvm-dsymutil missing AT_location for swift variables #4503

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swift-ci opened this issue Oct 3, 2017 · 5 comments
Closed

[SR-6046] DWARF generated by llvm-dsymutil missing AT_location for swift variables #4503

swift-ci opened this issue Oct 3, 2017 · 5 comments
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bug Something isn't working Compiler LLDB for Swift

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swift-ci commented Oct 3, 2017

Previous ID SR-6046
Radar None
Original Reporter fjricci (JIRA User)
Type Bug
Status Resolved
Resolution Done
Environment

macOS 10.12, Xcode 9.0.0

Additional Detail from JIRA
Votes 0
Component/s Compiler, LLDB for Swift
Labels Bug
Assignee fjricci (JIRA)
Priority Medium

md5: 09f90002185afba619fe232e126ea900

Issue Description:

Xcode's dsymutil creates DWARF locations correctly for swift variables, while llvm-dsymutil does not. This breaks debugging in swift-lldb, as variables without locations will fail to print.

$ cat /tmp/test.swift
let x = 42
print("x = (x)")

$ swiftc /tmp/test.swift  -g -Onone -sdk "/Applications/Xcode_9.0.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk" -o /tmp/test -save-temps

$ llvm-dsymutil /tmp/test -o /tmp/test-llvm.dSYM

$ "/Applications/Xcode_9.0.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/dsymutil"  /tmp/test -o /tmp/test-xcode.dSYM

$ dwarfdump /tmp/test-llvm.dSYM/Contents/Resources/DWARF/test | grep "AT_name( \"x\" )" -A5
                     AT_name( "x" )
                     AT_type( {0x00000093} ( Int ) )
                     AT_external( true )
                     AT_decl_file( "/private/tmp/test.swift" )
                     AT_decl_line( 1 )
                     AT_location( [0x0000000000000000] )

$ dwarfdump /tmp/test-xcode.dSYM/Contents/Resources/DWARF/test | grep "AT_name( \"x\" )" -A5
                     AT_name( "x" )
                     AT_type( {0x00000093} ( Int ) )
                     AT_external( true )
                     AT_decl_file( "/private/tmp/test.swift" )
                     AT_decl_line( 1 )
                     AT_location( [0x0000000100004628] )
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swift-ci commented Oct 3, 2017

Comment by Francis Ricci (JIRA)

Looks like the issue is an incorrect binAddr, from dsymutil -verbose:

llvm-dsymutil:

  • { sym: __Tv14test1xSi, objAddr: 0x0000000000000B10, binAddr: 0x0000000000000000, size: 0x00000000 }

xcode dsymutil:

  • { sym: __Tv14test1xSi, objAddr: 0x0000000000000B10, binAddr: 0x0000000100004628, size: 0x00000000 }

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swift-ci commented Oct 3, 2017

Comment by Francis Ricci (JIRA)

0x0000000100004628 looks like the start of _DATA,_common:

$ llvm-readobj /tmp/test -macho-segment -sections | grep 100004628 -B4
Section {
Index: 21
Name: __common (5F 5F 63 6F 6D 6D 6F 6E 00 00 00 00 00 00 00 00)
Segment: __DATA (5F 5F 44 41 54 41 00 00 00 00 00 00 00 00 00 00)
Address: 0x100004628

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swift-ci commented Oct 3, 2017

Comment by Francis Ricci (JIRA)

Appears to be because MachOObjectFile::symbols().getFlags() is returning SymbolRef::SF_None for all of the global symbols, which means they don't end up in the global symbol mapping.

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swift-ci commented Oct 5, 2017

Comment by Francis Ricci (JIRA)

https://reviews.llvm.org/D38587

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swift-ci commented Oct 6, 2017

Comment by Francis Ricci (JIRA)

Committed as llvm revision r315082

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 7, 2022
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