[lld] [llvm] [Symbolizer] Support for Missing Line Numbers. (PR #82240)

[David Blaikie via llvm-commits]

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+##  Test the "--skip-line-zero" option.
+##
+##  This test uses handcrafted assembly to produce the following line table:
+##  Address            Line   Column File   ISA Discriminator OpIndex Flags
+##  ------------------ ------ ------ ------ --- ------------- ------- -------------
+##  0x0000000000001710      1      0      1   0             0       0
+##  0x0000000000001714      0      0      1   0             0       0
+##  0x0000000000001719      1      2      1   0             0       0
+##  0x000000000000171b      1      2      1   0             0       0  end_sequence
+##  0x00000000000016c0      0      0      1   0             0       0
+##  0x00000000000016cf      2      0      1   0             0       0
+##  0x00000000000016d4      0      0      1   0             0       0
+##  0x00000000000016d9      0      0      1   0             0       0
+##  0x00000000000016df      0      0      1   0             0       0  end_sequence
+
+# REQUIRES: x86-registered-target
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+
+## Check that without '--skip-line-zero', line zero is displayed for a line-table entry which has no source correspondence.
+# RUN: llvm-symbolizer --obj=%t.o 0x16d4 | FileCheck --strict-whitespace --match-full-lines --check-prefix=DISABLE %s
+
+# DISABLE:main
+# DISABLE-NEXT:main.c:0:0
+
+## Check that the '--skip-line-zero' does not cross sequence boundaries.
+## If it fails to find in the current sequence then line zero is returned for the queried address.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero 0x16c0 | FileCheck --strict-whitespace --match-full-lines --check-prefix=FAIL-ACROSS-SEQ %s
+
+# FAIL-ACROSS-SEQ:main
+# FAIL-ACROSS-SEQ-NEXT:main.c:0:0
+
+## Check that with '--skip-line-zero', the last non-zero line in the current sequence is displayed.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero 0x1717 | FileCheck --strict-whitespace --match-full-lines --check-prefix=WITHIN-SEQ %s
+
+# WITHIN-SEQ:foo
+# WITHIN-SEQ-NEXT:main.c:1:0 (approximate)
+
+## Check that with '--skip-line-zero', multiple line zero rows are skipped within the current sequence.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero 0x16d9 | FileCheck --strict-whitespace --match-full-lines --check-prefix=MULTIPLE-ROWS %s
+
+# MULTIPLE-ROWS:main
+# MULTIPLE-ROWS-NEXT:main.c:2:0 (approximate)
+
+## Check that '--skip-line-zero' only affects the line zero addresses when more than one address is specified.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero 0x16d4 0x1719 | FileCheck --strict-whitespace --match-full-lines --check-prefixes=ENABLE,NO-APPROX %s
+
+# ENABLE:main
+# ENABLE-NEXT:main.c:2:0 (approximate)
+# NO-APPROX:foo
+# NO-APPROX-NEXT:main.c:1:2
+
+## Check to ensure that '--skip-line-zero' with '--verbose' enabled displays approximate flag in verbose ouptut.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero --verbose 0x1717 | FileCheck --strict-whitespace --match-full-lines --check-prefix=VERBOSE %s
+
+# VERBOSE:foo
+# VERBOSE-NEXT:  Filename: main.c
+# VERBOSE-NEXT:  Function start filename: main.c
+# VERBOSE-NEXT:  Function start line: 1
+# VERBOSE-NEXT:  Function start address: 0x1710
+# VERBOSE-NEXT:  Line: 1
+# VERBOSE-NEXT:  Column: 0
+# VERBOSE-NEXT:  Approximate: true
+
+## Check to ensure that '--skip-line-zero' with '--output-style=JSON' displays approximate flag in JSON output.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero --output-style=JSON 0x1717 | FileCheck --strict-whitespace --match-full-lines --check-prefix=JSON %s
+
+# JSON:[{"Address":"0x1717","ModuleName":"{{.*}}{{[/|\]+}}test{{[/|\]+}}tools{{[/|\]+}}llvm-symbolizer{{[/|\]+}}Output{{[/|\]+}}skip-line-zero.s.tmp.o","Symbol":[{"Approximate":true,"Column":0,"Discriminator":0,"FileName":"main.c","FunctionName":"foo","Line":1,"StartAddress":"0x1710","StartFileName":"main.c","StartLine":1}]}]
+
+## main.c
+## __attribute__((section("def"))) int foo() { return 1234; }
+## int main(void) { return foo()+5678; }
+##
+## Generated using
+## clang -S -gdwarf-4 --target=x86_64-pc-linux -fdebug-prefix-map=/tmp="" main.c -o main.s
+##
+## Sections belonging to code segment(.text) are removed. Sections related to debug information(other than .debug_line) are modified. Section .debug_line is handwritten.
+
+	.section	.debug_abbrev,"", at progbits
----------------
dwblaikie wrote:

I might've asked before, but double checking: Can we remove all the other debug info and just leave the line table? Since this is now basically entirely hand crafted there's no regeneration convenience of leaving this in here, I tihnk - and the symbolizer should work correctly/sufficiently for this feature with only a line table?

https://github.com/llvm/llvm-project/pull/82240