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

[via llvm-commits]

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+##  Test  --skip-line-zero option.
+##
+##  This test illustrates the usage of handcrafted assembly to produce the following line table.
+##  Address            Line   Column File   ISA Discriminator OpIndex Flags
+##  ------------------ ------ ------ ------ --- ------------- ------- -------------
+##  0x0000000000001710      1      0      2   0             0       0  is_stmt
+##  0x0000000000001717      0     17      2   0             0       0  is_stmt prologue_end
+##  0x000000000000171a      2     15      2   0             0       0
+##  0x000000000000171f      2      3      2   0             0       0  epilogue_begin
+##  0x0000000000001721      2      3      2   0             0       0  end_sequence
+##  0x00000000000016c0      0      0      1   0             0       0  is_stmt
+##  0x00000000000016cf      3     29      1   0             0       0  is_stmt prologue_end
+##  0x00000000000016d5      0     25      1   0             0       0
+##  0x00000000000016da      3     18      1   0             0       0  epilogue_begin
+##  0x00000000000016e0      3     18      1   0             0       0  end_sequence
+
+# REQUIRES: x86-registered-target
+
+# RUN: rm -rf %t && split-file %s %t && cd %t
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux --fdebug-prefix-map=%t="" %s -o %t.o
+
+## Check that without '--skip-line-zero', line number zero is displayed for the line-table entry which has no source correspondence.
+# RUN: llvm-symbolizer --obj=%t.o 0x16d5 | FileCheck --strict-whitespace --match-full-lines --check-prefix=APPROX-DISABLE %s
+
+# APPROX-DISABLE:main
+# APPROX-DISABLE-NEXT:main.c:0:25
+
+## Check that with '--skip-line-zero', the last non-zero line in the current sequence is displayed.
+## If it fails to find in the current sequence then return the original computed line-zero for the queried address.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero 0x16c0 | FileCheck --strict-whitespace --match-full-lines --check-prefix=APPROX-FAIL-ACROSS-SEQ %s
+
+# APPROX-FAIL-ACROSS-SEQ:main
+# APPROX-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=APPROX-WITHIN-SEQ %s
+
+# APPROX-WITHIN-SEQ:foo
+# APPROX-WITHIN-SEQ-NEXT:definitions.c:1:0 (approximate)
+
+## Check to ensure that '--skip-line-zero' only affects addresses having line-zero when more than one address is specified.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero 0x16d5 0x16da | FileCheck --strict-whitespace --match-full-lines --check-prefixes=APPROX-ENABLE,NO-APPROX %s
+
+# APPROX-ENABLE:main
+# APPROX-ENABLE-NEXT:main.c:3:29 (approximate)
+# NO-APPROX:main
+# NO-APPROX-NEXT:main.c:3:18
+
+## Check to ensure that '--skip-line-zero' with '--verbose' enabled displays correct approximate flag in verbose ouptut.
+# RUN: llvm-symbolizer --obj=%t.o --skip-line-zero --verbose 0x1717 | FileCheck --strict-whitespace --match-full-lines --check-prefix=APPROX-VERBOSE %s
+
+# APPROX-VERBOSE:foo
+# APPROX-VERBOSE-NEXT:  Filename: definitions.c
+# APPROX-VERBOSE-NEXT:  Function start filename: definitions.c
+# APPROX-VERBOSE-NEXT:  Function start line: 1
+# APPROX-VERBOSE-NEXT:  Function start address: 0x1710
+# APPROX-VERBOSE-NEXT:  Line: 1
+# APPROX-VERBOSE-NEXT:  Column: 0
+# APPROX-VERBOSE-NEXT:  Approximate: true
+
+## Check to ensure that '--skip-line-zero' with '--output-style=JSON' displays correct 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=APPROX-JSON %s
+
+# APPROX-JSON:[{"Address":"0x1717","ModuleName":"{{.*}}{{[/|\]+}}test{{[/|\]+}}tools{{[/|\]+}}llvm-symbolizer{{[/|\]+}}Output{{[/|\]+}}skip-line-zero.s.tmp.o","Symbol":[{"Approximate":true,"Column":0,"Discriminator":0,"FileName":"definitions.c","FunctionName":"foo","Line":1,"StartAddress":"0x1710","StartFileName":"definitions.c","StartLine":1}]}]
+
+#--- definitions.c
+#__attribute__((section("def"))) unsigned int foo(unsigned int x) {
+#  return 1234 + x;
+#}
+
+#--- main.c
+#include "definitions.c"
+#unsigned int x = 1000;
+#int main(void) { return foo(x); }
+
+#--- gen
+#clang -S -gdwarf-4 --target=x86_64-pc-linux -fdebug-prefix-map=/proc/self/cwd="" -fdebug-prefix-map=./="" main.c -o main.s
+
+#sed -i '1,72d' main.s                                # Delete .text and .def sections
----------------
bd1976bris wrote:

Nice use of sed and #--- gen. However, I think that this editing via sed is fragile as it is e.g. hard coding the line numbers. It might be better to just have assembly directly here and skip the "gen" stuff? You could still include the source code you started from in a comment?

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