From: Aaron Merey <amerey@redhat.com>
Date: Sat, 10 Feb 2024 02:10:19 +0000 (-0500)
Subject: Handle DW_AT_decl_file 0
X-Git-Tag: elfutils-0.191~17
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=add63e0317b6e27dd4077b19e998e6c56a3becb5;p=thirdparty%2Felfutils.git

Handle DW_AT_decl_file 0

Modify dwarf_decl_file to support DW_AT_decl_file with value 0.

Because of inconsistencies in the DWARF 5 spec, it is ambiguous whether
DW_AT_decl_file value 0 is a valid .debug_line file table index for the
main source file or if it means that there is no source file specified.

dwarf_decl_file interprets DW_AT_decl_file 0 as meaning no source file
is specified.  This works with DWARF 5 produced by gcc, which duplicates
the main source file name at index 0 and 1 of the file table and avoids
using DW_AT_decl_file 0.

However clang uses DW_AT_decl_file 0 for the main source index with no
duplication at another index.  In this case dwarf_decl_file will be
unable to find the file name of the main file.

This patch changes dwarf_decl_file to treat DW_AT_decl_file 0 as a normal
index into the file table, allowing it to work with DWARF 5 debuginfo
produced by clang.

As for earlier DWARF versions which exclusively use DW_AT_decl_file 0
to indicate that no source file is specified, dwarf_decl_file will now
return the name "???" if called on a DIE with DW_AT_decl_file 0.

https://sourceware.org/bugzilla/show_bug.cgi?id=31111

Signed-off-by: Aaron Merey <amerey@redhat.com>
---

diff --git a/libdw/dwarf_decl_file.c b/libdw/dwarf_decl_file.c
index 75662a334..7dde4af07 100644
--- a/libdw/dwarf_decl_file.c
+++ b/libdw/dwarf_decl_file.c
@@ -48,13 +48,6 @@ dwarf_decl_file (Dwarf_Die *die)
 			       &idx) != 0)
     return NULL;
 
-  /* Zero means no source file information available.  */
-  if (idx == 0)
-    {
-      __libdw_seterrno (DWARF_E_NO_ENTRY);
-      return NULL;
-    }
-
   /* Get the array of source files for the CU.  */
   struct Dwarf_CU *cu = attr_mem.cu;
   if (cu->lines == NULL)
@@ -70,8 +63,8 @@ dwarf_decl_file (Dwarf_Die *die)
 
   if (cu->lines == (void *) -1l)
     {
-      /* If the file index is not zero, there must be file information
-	 available.  */
+      /* If DW_AT_decl_file was present, there should be file information
+	available.  */
       __libdw_seterrno (DWARF_E_INVALID_DWARF);
       return NULL;
     }
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 13bd9d568..b075e3c36 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -634,7 +634,8 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh run-ar.sh \
 	     testfile-largealign.o.bz2 run-strip-largealign.sh \
 	     run-funcretval++11.sh \
 	     test-ar-duplicates.a.bz2 \
-	     run-dwfl-core-noncontig.sh testcore-noncontig.bz2
+	     run-dwfl-core-noncontig.sh testcore-noncontig.bz2 \
+	     testfile-dwarf5-line-clang.bz2
 
 
 if USE_VALGRIND
diff --git a/tests/run-allfcts.sh b/tests/run-allfcts.sh
index 9c0a55d86..4dd0284a8 100755
--- a/tests/run-allfcts.sh
+++ b/tests/run-allfcts.sh
@@ -170,4 +170,21 @@ testrun_compare ${abs_builddir}/allfcts testfile-lto-gcc9 <<\EOF
 /home/mark/src/tests/testfile-lto-main.c:6:main
 EOF
 
+# = dwarf5-line.c =
+# int
+# main (int argc, char **argv)
+# {
+#   return 0;
+# }
+
+# Using clang version 17.0.4 (Fedora 17.0.4-1.fc39)
+# clang -gdwarf-5 -o testfile-dwarf5-line-clang dwarf5-line.c
+
+testfiles testfile-dwarf5-line-clang
+
+# Check that dwarf_decl_file can handle .debug_line file table index 0
+testrun_compare ${abs_builddir}/allfcts testfile-dwarf5-line-clang <<\EOF
+/home/amerey/test/dwarf5-line.c:2:main
+EOF
+
 exit 0
diff --git a/tests/testfile-dwarf5-line-clang.bz2 b/tests/testfile-dwarf5-line-clang.bz2
new file mode 100755
index 000000000..bdd66e963
Binary files /dev/null and b/tests/testfile-dwarf5-line-clang.bz2 differ