[Bug lto/56532] New: valgrind errors with -flto

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56532

             Bug #: 56532
           Summary: valgrind errors with -flto
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jakub@gcc.gnu.org


valgrind --leak-check=full --track-origins=yes --db-attach=yes ./cc1plus
pr46984.C -O -fipa-cp -fno-early-inlining -flto -quiet
gives:
==5852== Conditional jump or move depends on uninitialised value(s)
==5852==    at 0x1205C84: bp_pack_var_len_unsigned(bitpack_d*, unsigned long)
(data-streamer.c:36)
==5852==    by 0xB2144D: lto_output_edge(lto_simple_output_block*,
cgraph_edge*, lto_symtab_encoder_d*) (lto-cgraph.c:277)
==5852==    by 0xB2285F: output_outgoing_cgraph_edges(cgraph_edge*,
lto_simple_output_block*, lto_symtab_encoder_d*) (lto-cgraph.c:651)
==5852==    by 0xB22F9E: output_symtab() (lto-cgraph.c:840)
==5852==    by 0xB2DCD1: lto_output() (lto-streamer-out.c:1000)
==5852==    by 0xB730F7: ipa_write_summaries_2(opt_pass*, lto_out_decl_state*)
(passes.c:2408)
==5852==    by 0xB731E6: ipa_write_summaries_1(lto_symtab_encoder_d*)
(passes.c:2438)
==5852==    by 0xB733B6: ipa_write_summaries() (passes.c:2492)
==5852==    by 0x893292: ipa_passes() (cgraphunit.c:1905)
==5852==    by 0x8936B7: compile() (cgraphunit.c:1991)
==5852==    by 0x8939B7: finalize_compilation_unit() (cgraphunit.c:2119)
==5852==    by 0x647071: cp_write_global_declarations() (decl2.c:4318)
==5852==  Uninitialised value was created by a client request
==5852==    at 0x7F654A: ggc_internal_alloc_stat(unsigned long)
(ggc-page.c:1339)
==5852==    by 0x886F18: cgraph_create_edge_1(cgraph_node*, cgraph_node*,
gimple_statement_d*, long, int) (cgraph.c:793)
==5852==    by 0x88714F: cgraph_create_edge(cgraph_node*, cgraph_node*,
gimple_statement_d*, long, int) (cgraph.c:838)
==5852==    by 0x88F6BF: cgraph_analyze_function(cgraph_node*)
(cgraphunit.c:630)
==5852==    by 0x8906C8: cgraph_analyze_functions() (cgraphunit.c:964)
==5852==    by 0x8939A8: finalize_compilation_unit() (cgraphunit.c:2110)
==5852==    by 0x647071: cp_write_global_declarations() (decl2.c:4318)
==5852==    by 0xC63E12: compile_file() (toplev.c:557)
==5852==    by 0xC65DB5: do_compile() (toplev.c:1876)
==5852==    by 0xC65F20: toplev_main(int, char**) (toplev.c:1952)
==5852==    by 0x12EC1CD: main (main.c:36)

273  uid = (!gimple_has_body_p (edge->caller->symbol.decl)
274 ? edge->lto_stmt_uid : gimple_uid (edge->call_stmt));

gimple_has_body_p is false (edge->call_stmt is NULL, DECL_STRUCT_FUNCTION
(edge->caller->symbol.decl) is NULL), and lto_stmt_uid is clearly
uninitialized.

When run under gdb rather than valgrind where you can't make interior calls:
b lto-cgraph.c:273 if !gimple_has_body_p (edge->caller->symbol.decl) &&
edge->lto_stmt_uid == 0xafafafaf
shows
(gdb) p debug_generic_stmt (edge->caller->symbol.decl)
_ZThn528_N1D3fooEv
(gdb) p debug_generic_stmt (edge->callee->symbol.decl)
*.LTHUNK0

Which also shows why I haven't seen any such failures in
gcc/testsuite/gcc/gcc.log, while tons of them in gcc/testsuite/g++/g++.log -
bet only thunks don't have body here and the code doesn't count with those.