[SR-3280] Package manager should link main swiftmodule in executables

[swift-ci]

Previous ID	SR-3280
Radar	rdar://problem/29228963
Original Reporter	nerakhon (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	5
Component/s	Package Manager
Labels	Bug
Assignee	@aciidb0mb3r
Priority	Medium

md5: cd20a7b4bf80be0100567d8c27f63fe5

is blocked by:

• SR-2660 Teach the driver to accept multiple swiftmodules as linker inputs, for static linking

is duplicated by:

• SR-2192 Swift's LLDB cannot import system modules and prevents debugging
• SR-11543 lldb doesn't work in tests: error: warning: failed to get module "NIO" from AST context

relates to:

• SR-3863 swift emits a temporary swiftmodule when swiftmodule of main module is passed with -emit-executable
• SR-11543 lldb doesn't work in tests: error: warning: failed to get module "NIO" from AST context

Issue Description:

Upon creation of empty packgage of type --executable when I build the package via swift build. I receive a binary that works, but isn't debuggable.

lldb .build/debug/lldb-test

(lldb) target create ".build/debug/lldb-test"
Current executable set to '.build/debug/lldb-test' (x86_64).
(lldb) breakpoint set -f main.swift -l 3
Breakpoint 1: where = lldb-test`main + 81 at main.swift:3, address = 0x0000000000400e81
(lldb) r
Process 30195 launched: '/home/janpaul/src/lldb-test/.build/debug/lldb-test' (x86_64)
Process 30195 stopped

• thread Add missing steps to creating a C library package. #1: tid = 30195, 0x0000000000400e81 lldb-test`main + 81 at main.swift:3, name = 'lldb-test', stop reason = breakpoint 1.1
  frame #0: 0x0000000000400e81 lldb-test`main + 81 at main.swift:3
  1 import Foundation
  2
  -> 3 let swifty="Swift is cool"
  4
  5 print(swifty)
  6
  7 exit(0)
  (lldb) n
  Process 30195 stopped

• thread Add missing steps to creating a C library package. #1: tid = 30195, 0x0000000000400ea4 lldb-test`main + 116 at main.swift:5, name = 'lldb-test', stop reason = step over
  frame #0: 0x0000000000400ea4 lldb-test`main + 116 at main.swift:5
  2
  3 let swifty="Swift is cool"
  4
  -> 5 print(swifty)
  6
  7 exit(0)
  (lldb) po swifty
  error: in auto-import:
  failed to get module 'lldb_test' from AST context

[swift-ci]

Comment by Jan Paul (JIRA)

The problem doesnt' exist when I build the main.swift manually via swiftc -g main.swift just in case there was doubt 😉

[aciidgh]

This looks like a problem with the compiler or lldb. lldb doesn't work when we use create executable via objects:

$ cat main.swift
let str = "Hello world"
print(str)

This works:
$ swiftc -g -o sample -emit-executable main.swift
$ lldb sample
(lldb) b main.swift:2
(lldb) r
(lldb) po str
"Hello world"

This doesn't:
$ swiftc -module-name sample -g -emit-object -c main.swift
$ swiftc -g -o sample -emit-executable main.o
$ lldb sample
(lldb) b main.swift:2
(lldb) r
(lldb) po str
error: in auto-import:
failed to get module 'sample' from AST context

--
$ swift --version
Swift version 3.0-dev (LLVM 8226908317, Clang e82f59cafd, Swift ce722fe0a5)
Target: x86_64-unknown-linux-gnu
$ lldb --version
lldb version 4.0.0 (git@github.com:apple/swift-lldb.git revision 85e9e3cafb8cd2c58e1197510f48ac13e92fbde3 clang revision e82f59cafd6c10e2063bc46b53f99b96d397371b llvm revision 822690831754af558dabf4048dd7da5ed2ff2f00)

Toolchain: swift-DEVELOPMENT-SNAPSHOT-2016-11-15-a-ubuntu16.04

[belkadan]

That's correct. Swift needs to include the swiftmodule in the debug info, so if you link in a separate step it doesn't have a chance to do that. Take a look at what swiftc -### does.

[swift-ci]

Comment by Jin Mingling (JIRA)

this seem more critical because the SPM debug outcome can not be debugged.

do we have some workaround, such as some flag to let lldb(swift version) load swiftmodule info by manual?

[aciidgh]

@belkadan Thanks, looks like if you pass swiftmodule in link step (with module name) it debugs properly.
#856

[ddunbar]

This is fixed right?

[aciidgh]

Nope, see PR

[aciidgh]

#933

[aciidgh]

The problem is package manager need to link main swiftmodule with the executable to make them debuggable. The PR #933 on package manager is currently blocked by SR-3863 (duped by SR-2660).

It looks like the debugging works fine without linking swiftmodule if there is a search path to the system module package. So if you invoke swiftpm with it, debugging will work:
$ swift build -Xcc -I/path/to/system/module

or if you convert the system module to a "fake" Clang module, swiftpm will automatically add a search path. This is of course not the correct solution but maybe is useful in the mean time.

[weissi]

@aciidb0mb3r/@neonichu any updates on this? Apparently this is blocking all debugging on Linux and also partially on macOS.

[weissi]

see https://bugs.swift.org/browse/SR-11543 🙁

[abertelrud]

I believe this is fixed in Swift 5.3. Comments in SR-11543 also suggest that this is fixed.