58e41976fe
- Fix for bsc#1146475 [bsc#1146475, swo#24971 ] * gdb-symtab-prefer-var-def-over-decl.patch - Fix for bsc#1146167 [bsc#1146167, swo#24956] * gdb-only-force-interp_console-ui_out-for-breakpoint-commands-in-mi-mode.patch OBS-URL: https://build.opensuse.org/request/show/746178 OBS-URL: https://build.opensuse.org/package/show/devel:gcc/gdb?expand=0&rev=235
233 lines
7.5 KiB
Diff
233 lines
7.5 KiB
Diff
[gdb/symtab] Prefer var def over decl
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Consider the DWARF as generated by gcc with the tentative patch to fix gcc
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PR91507 - "wrong debug for completed array with previous incomplete
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declaration":
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...
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<1><f4>: Abbrev Number: 2 (DW_TAG_array_type)
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<f5> DW_AT_type : <0xff>
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<f9> DW_AT_sibling : <0xff>
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<2><fd>: Abbrev Number: 3 (DW_TAG_subrange_type)
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<2><fe>: Abbrev Number: 0
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<1><ff>: Abbrev Number: 4 (DW_TAG_pointer_type)
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<100> DW_AT_byte_size : 8
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<101> DW_AT_type : <0x105>
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<1><105>: Abbrev Number: 5 (DW_TAG_base_type)
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<106> DW_AT_byte_size : 1
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<107> DW_AT_encoding : 6 (signed char)
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<108> DW_AT_name : (indirect string, offset: 0x19f): char
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<1><10c>: Abbrev Number: 6 (DW_TAG_variable)
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<10d> DW_AT_name : zzz
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<111> DW_AT_decl_file : 1
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<112> DW_AT_decl_line : 1
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<113> DW_AT_decl_column : 14
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<114> DW_AT_type : <0xf4>
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<118> DW_AT_external : 1
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<118> DW_AT_declaration : 1
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<1><118>: Abbrev Number: 2 (DW_TAG_array_type)
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<119> DW_AT_type : <0xff>
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<11d> DW_AT_sibling : <0x128>
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<1><12f>: Abbrev Number: 8 (DW_TAG_variable)
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<130> DW_AT_specification: <0x10c>
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<134> DW_AT_decl_line : 2
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<135> DW_AT_decl_column : 7
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<136> DW_AT_type : <0x118>
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<13a> DW_AT_location : 9 byte block: 3 30 10 60 0 0 0 0 0 (DW_OP_addr: 601030)
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...
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The DWARF will result in two entries in the symbol table, a decl with type
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char *[] and a def with type char*[2].
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When trying to print the value of zzz:
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...
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$ gdb a.spec.out -batch -ex "p zzz"
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...
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the decl (rather than the def) will be found in the symbol table, which is
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missing the location information, and consequently we get:
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...
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$1 = 0x601030 <zzz>
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...
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[ There is a fallback mechanism that finds the address of the variable in the
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minimal symbol table, but that's not used here, because the type of the decl
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does not specify a size. We could use the symbol size here to get the size
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of the type, but that's currently not done: PR exp/24989. Still, fixing that
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PR would not fix the generic case, where minimal symbol info is not
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available. ]
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Fix this by preferring defs over decls when searching in the symbol table.
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Build and reg-tested on x86_64-linux.
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[ The test-case is a bit simpler than the DWARF example listed above, because
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the new variable varval3 that is used is not listed in the minimal symbols, so
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there's no need to work around the fallback mechanism to trigger the problem. ]
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gdb/ChangeLog:
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2019-09-10 Tom de Vries <tdevries@suse.de>
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PR symtab/24971
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* block.c (best_symbol, better_symbol): New function.
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(block_lookup_symbol_primary): Prefer def over decl.
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gdb/testsuite/ChangeLog:
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2019-09-10 Tom de Vries <tdevries@suse.de>
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* gdb.dwarf2/varval.exp: Add decl before def test.
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Change-Id: Id92326cb8ef9903b121ef9e320658eb565d0f5a9
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---
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gdb/block.c | 68 +++++++++++++++++++++++++++++++++++--
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gdb/testsuite/gdb.dwarf2/varval.exp | 28 +++++++++++++--
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2 files changed, 92 insertions(+), 4 deletions(-)
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diff --git a/gdb/block.c b/gdb/block.c
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index 3192b33e9e9..37f9d4f8d21 100644
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--- a/gdb/block.c
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+++ b/gdb/block.c
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@@ -726,6 +726,43 @@ block_lookup_symbol (const struct block *block, const char *name,
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}
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}
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+/* Return true if symbol A is the best match possible for DOMAIN. */
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+
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+static bool
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+best_symbol (struct symbol *a, const domain_enum domain)
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+{
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+ return (SYMBOL_DOMAIN (a) == domain
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+ && SYMBOL_CLASS (a) != LOC_UNRESOLVED);
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+}
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+
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+/* Return symbol B if it is a better match than symbol A for DOMAIN.
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+ Otherwise return A. */
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+
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+static struct symbol *
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+better_symbol (struct symbol *a, struct symbol *b, const domain_enum domain)
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+{
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+ if (a == NULL)
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+ return b;
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+ if (b == NULL)
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+ return a;
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+
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+ if (SYMBOL_DOMAIN (a) == domain
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+ && SYMBOL_DOMAIN (b) != domain)
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+ return a;
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+ if (SYMBOL_DOMAIN (b) == domain
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+ && SYMBOL_DOMAIN (a) != domain)
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+ return b;
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+
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+ if (SYMBOL_CLASS (a) != LOC_UNRESOLVED
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+ && SYMBOL_CLASS (b) == LOC_UNRESOLVED)
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+ return a;
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+ if (SYMBOL_CLASS (b) != LOC_UNRESOLVED
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+ && SYMBOL_CLASS (a) == LOC_UNRESOLVED)
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+ return b;
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+
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+ return a;
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+}
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+
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/* See block.h. */
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struct symbol *
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@@ -747,7 +784,34 @@ block_lookup_symbol_primary (const struct block *block, const char *name,
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sym != NULL;
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sym = mdict_iter_match_next (lookup_name, &mdict_iter))
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{
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- if (SYMBOL_DOMAIN (sym) == domain)
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+ /* With the fix for PR gcc/debug/91507, we get for:
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+ ...
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+ extern char *zzz[];
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+ char *zzz[ ] = {
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+ "abc",
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+ "cde"
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+ };
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+ ...
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+ DWARF which will result in two entries in the symbol table, a decl
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+ with type char *[] and a def with type char *[2].
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+
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+ If we return the decl here, we don't get the value of zzz:
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+ ...
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+ $ gdb a.spec.out -batch -ex "p zzz"
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+ $1 = 0x601030 <zzz>
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+ ...
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+ because we're returning the symbol without location information, and
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+ because the fallback that uses the address from the minimal symbols
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+ doesn't work either because the type of the decl does not specify a
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+ size.
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+
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+ To fix this, we prefer def over decl in best_symbol and
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+ better_symbol.
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+
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+ In absence of the gcc fix, both def and decl have type char *[], so
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+ the only option to make this work is improve the fallback to use the
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+ size of the minimal symbol. Filed as PR exp/24989. */
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+ if (best_symbol (sym, domain))
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return sym;
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/* This is a bit of a hack, but symbol_matches_domain might ignore
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@@ -756,7 +820,7 @@ block_lookup_symbol_primary (const struct block *block, const char *name,
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exactly the same domain. PR 16253. */
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if (symbol_matches_domain (SYMBOL_LANGUAGE (sym),
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SYMBOL_DOMAIN (sym), domain))
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- other = sym;
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+ other = better_symbol (other, sym, domain);
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}
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return other;
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diff --git a/gdb/testsuite/gdb.dwarf2/varval.exp b/gdb/testsuite/gdb.dwarf2/varval.exp
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index 4711f4a24ae..fa3d90eb3d9 100644
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--- a/gdb/testsuite/gdb.dwarf2/varval.exp
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+++ b/gdb/testsuite/gdb.dwarf2/varval.exp
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@@ -51,7 +51,7 @@ Dwarf::assemble ${asm_file} {
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var_b_label var_c_label var_p_label var_bad_label \
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varval_label var_s_label var_untyped_label \
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var_a_abstract_label var_a_concrete_label \
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- varval2_label
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+ varval2_label varval3_decl_label varval3_def_label
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set int_size [get_sizeof "int" -1]
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@@ -165,6 +165,18 @@ Dwarf::assemble ${asm_file} {
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{DW_AT_location {DW_OP_addr [gdb_target_symbol "var_b"]} SPECIAL_expr}
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}
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+ varval3_decl_label: DW_TAG_variable {
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+ {DW_AT_name "varval3"}
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+ {DW_AT_type :${int_label}}
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+ {DW_AT_external 1 DW_FORM_flag}
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+ {DW_AT_declaration 1 DW_FORM_flag}
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+ }
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+ varval3_def_label: DW_TAG_variable {
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+ {DW_AT_name "varval3"}
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+ {DW_AT_external 1 DW_FORM_flag}
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+ {DW_AT_type :${int_label}}
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+ {DW_AT_location {DW_OP_addr [gdb_target_symbol "var_a"]} SPECIAL_expr}
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+ }
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DW_TAG_subprogram {
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{MACRO_AT_func { "main" "${srcdir}/${subdir}/${srcfile}" }}
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{DW_AT_type :${int_label}}
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@@ -274,7 +286,19 @@ if ![runto_main] {
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}
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gdb_test "print varval" "= 8"
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-gdb_test "print varval2" "= 8"
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+#gdb_test "print varval2" "= 8"
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+set test "print varval2"
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+set pass_pattern "= 8"
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+set kfail_pattern "value has been optimized out"
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+gdb_test_multiple $test "" {
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+ -re "\[\r\n\]*(?:$pass_pattern)\[\r\n\]+$gdb_prompt $" {
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+ pass $test
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+ }
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+ -re "\[\r\n\]*(?:$kfail_pattern)\[\r\n\]+$gdb_prompt $" {
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+ kfail gdb/24515 $test
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+ }
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+}
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+gdb_test "print varval3" "= 8"
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gdb_test "print constval" "= 53"
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gdb_test "print mixedval" "= 42"
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gdb_test "print pointerval" "= \\(int \\*\\) $hex <var_b>"
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