Alexander Prendota
262 lines
7.7 KiB
Markdown
262 lines
7.7 KiB
Markdown
## Debugging
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Currently the Kotlin/Native compiler produces debug info compatible with the DWARF 2 specification, so modern debugger tools can
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perform the following operations:
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- breakpoints
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- stepping
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- inspection of type information
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- variable inspection
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### Producing binaries with debug info with Kotlin/Native compiler
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To produce binaries with the Kotlin/Native compiler it's sufficient to use the ``-g`` option on the command line.<br/>
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_Example:_
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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0:b-debugger-fixes:minamoto@unit-703(0)# cat - > hello.kt
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fun main(args: Array<String>) {
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println("Hello world")
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println("I need your clothes, your boots and your motocycle")
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}
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0:b-debugger-fixes:minamoto@unit-703(0)# dist/bin/konanc -g hello.kt -o terminator
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KtFile: hello.kt
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0:b-debugger-fixes:minamoto@unit-703(0)# lldb terminator.kexe
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(lldb) target create "terminator.kexe"
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Current executable set to 'terminator.kexe' (x86_64).
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(lldb) b kfun:main(kotlin.Array<kotlin.String>)
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Breakpoint 1: where = terminator.kexe`kfun:main(kotlin.Array<kotlin.String>) + 4 at hello.kt:2, address = 0x00000001000012e4
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(lldb) r
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Process 28473 launched: '/Users/minamoto/ws/.git-trees/debugger-fixes/terminator.kexe' (x86_64)
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Process 28473 stopped
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* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
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frame #0: 0x00000001000012e4 terminator.kexe`kfun:main(kotlin.Array<kotlin.String>) at hello.kt:2
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1 fun main(args: Array<String>) {
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-> 2 println("Hello world")
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3 println("I need your clothes, your boots and your motocycle")
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4 }
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(lldb) n
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Hello world
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Process 28473 stopped
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* thread #1, queue = 'com.apple.main-thread', stop reason = step over
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frame #0: 0x00000001000012f0 terminator.kexe`kfun:main(kotlin.Array<kotlin.String>) at hello.kt:3
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1 fun main(args: Array<String>) {
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2 println("Hello world")
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-> 3 println("I need your clothes, your boots and your motocycle")
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4 }
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(lldb)
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```
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</div>
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### Breakpoints
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Modern debuggers provide several ways to set a breakpoint, see below for a tool-by-tool breakdown:
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#### lldb
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- by name
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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(lldb) b -n kfun:main(kotlin.Array<kotlin.String>)
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Breakpoint 4: where = terminator.kexe`kfun:main(kotlin.Array<kotlin.String>) + 4 at hello.kt:2, address = 0x00000001000012e4
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```
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</div>
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_``-n`` is optional, this flag is applied by default_
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- by location (filename, line number)
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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(lldb) b -f hello.kt -l 1
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Breakpoint 1: where = terminator.kexe`kfun:main(kotlin.Array<kotlin.String>) + 4 at hello.kt:2, address = 0x00000001000012e4
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```
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</div>
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- by address
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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(lldb) b -a 0x00000001000012e4
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Breakpoint 2: address = 0x00000001000012e4
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```
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</div>
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- by regex, you might find it useful for debugging generated artifacts, like lambda etc. (where used ``#`` symbol in name).
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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3: regex = 'main\(', locations = 1
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3.1: where = terminator.kexe`kfun:main(kotlin.Array<kotlin.String>) + 4 at hello.kt:2, address = terminator.kexe[0x00000001000012e4], unresolved, hit count = 0
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```
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</div>
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#### gdb
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- by regex
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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(gdb) rbreak main(
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Breakpoint 1 at 0x1000109b4
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struct ktype:kotlin.Unit &kfun:main(kotlin.Array<kotlin.String>);
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```
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</div>
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- by name __unusable__, because ``:`` is a separator for the breakpoint by location
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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(gdb) b kfun:main(kotlin.Array<kotlin.String>)
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No source file named kfun.
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Make breakpoint pending on future shared library load? (y or [n]) y
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Breakpoint 1 (kfun:main(kotlin.Array<kotlin.String>)) pending
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```
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</div>
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- by location
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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(gdb) b hello.kt:1
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Breakpoint 2 at 0x100001704: file /Users/minamoto/ws/.git-trees/hello.kt, line 1.
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```
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</div>
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- by address
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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(gdb) b *0x100001704
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Note: breakpoint 2 also set at pc 0x100001704.
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Breakpoint 3 at 0x100001704: file /Users/minamoto/ws/.git-trees/hello.kt, line 2.
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```
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</div>
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### Stepping
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Stepping functions works mostly the same way as for C/C++ programs
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### Variable inspection
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Variable inspections for var variables works out of the box for primitive types.
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For non-primitive types there are custom pretty printers for lldb in
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`konan_lldb.py`:
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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λ cat main.kt | nl
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1 fun main(args: Array<String>) {
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2 var x = 1
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3 var y = 2
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4 var p = Point(x, y)
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5 println("p = $p")
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6 }
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7 data class Point(val x: Int, val y: Int)
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λ lldb ./program.kexe -o 'b main.kt:5' -o
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(lldb) target create "./program.kexe"
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Current executable set to './program.kexe' (x86_64).
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(lldb) b main.kt:5
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Breakpoint 1: where = program.kexe`kfun:main(kotlin.Array<kotlin.String>) + 289 at main.kt:5, address = 0x000000000040af11
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(lldb) r
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Process 4985 stopped
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* thread #1, name = 'program.kexe', stop reason = breakpoint 1.1
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frame #0: program.kexe`kfun:main(kotlin.Array<kotlin.String>) at main.kt:5
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2 var x = 1
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3 var y = 2
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4 var p = Point(x, y)
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-> 5 println("p = $p")
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6 }
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7
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8 data class Point(val x: Int, val y: Int)
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Process 4985 launched: './program.kexe' (x86_64)
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(lldb) fr var
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(int) x = 1
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(int) y = 2
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(ObjHeader *) p = 0x00000000007643d8
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(lldb) command script import dist/tools/konan_lldb.py
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(lldb) fr var
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(int) x = 1
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(int) y = 2
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(ObjHeader *) p = Point(x=1, y=2)
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(lldb) p p
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(ObjHeader *) $2 = Point(x=1, y=2)
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(lldb)
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```
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</div>
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Getting representation of the object variable (var) could also be done using the
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built-in runtime function `Konan_DebugPrint` (this approach also works for gdb,
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using a module of command syntax):
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<div class="sample" markdown="1" theme="idea" mode="shell">
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```bash
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0:b-debugger-fixes:minamoto@unit-703(0)# cat ../debugger-plugin/1.kt | nl -p
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1 fun foo(a:String, b:Int) = a + b
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2 fun one() = 1
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3 fun main(arg:Array<String>) {
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4 var a_variable = foo("(a_variable) one is ", 1)
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5 var b_variable = foo("(b_variable) two is ", 2)
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6 var c_variable = foo("(c_variable) two is ", 3)
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7 var d_variable = foo("(d_variable) two is ", 4)
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8 println(a_variable)
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9 println(b_variable)
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10 println(c_variable)
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11 println(d_variable)
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12 }
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0:b-debugger-fixes:minamoto@unit-703(0)# lldb ./program.kexe -o 'b -f 1.kt -l 9' -o r
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(lldb) target create "./program.kexe"
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Current executable set to './program.kexe' (x86_64).
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(lldb) b -f 1.kt -l 9
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Breakpoint 1: where = program.kexe`kfun:main(kotlin.Array<kotlin.String>) + 463 at 1.kt:9, address = 0x0000000100000dbf
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(lldb) r
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(a_variable) one is 1
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Process 80496 stopped
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* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
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frame #0: 0x0000000100000dbf program.kexe`kfun:main(kotlin.Array<kotlin.String>) at 1.kt:9
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6 var c_variable = foo("(c_variable) two is ", 3)
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7 var d_variable = foo("(d_variable) two is ", 4)
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8 println(a_variable)
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-> 9 println(b_variable)
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10 println(c_variable)
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11 println(d_variable)
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12 }
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Process 80496 launched: './program.kexe' (x86_64)
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(lldb) expression -- Konan_DebugPrint(a_variable)
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(a_variable) one is 1(KInt) $0 = 0
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(lldb)
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```
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</div>
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### Known issues
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- performance of Python bindings.
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_Note:_ Supporting the DWARF 2 specification means that the debugger tool recognizes Kotlin as C89, because before the DWARF 5 specification, there is no identifier for the Kotlin language type in specification.
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