| Summary: | unused argc/argv missing their DW_AT_location | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Jan Kratochvil <jkratochvil> |
| Component: | debug | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | dodji, gcc-bugs |
| Priority: | P3 | ||
| Version: | unknown | ||
| Target Milestone: | --- | ||
| Host: | Target: | i686-pc-linux-gnu | |
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | ||
This is caused by the stack realignment in i?86 main, the way it is currently implemented is that address of first argument is loaded into %ecx and then the stack is realigned. The pseudo register which shows in the argument's RTL is that cfun->machine->force_align_arg_pointer (aka %ecx) copied into a pseudo. Hello, I can't reproduce this neither on 4.3 nor trunk branch. In both branch, the variables have the DW_AT_location attribute. Please see below the attached dwarf output. Fedora gcc-4.3.2-6.x86_64 with -m32 is still buggy as described in the Comment 0. But HEAD works OK now (-m32) so closing, thanks for the test: GNU C (GCC) version 4.4.0 20081007 (experimental) (x86_64-unknown-linux-gnu) compiled by GNU C version 4.4.0 20081007 (experimental), GMP version 4.2.2, MPFR version 2.3.1. |
`main' function (the function with specific prologue/epilogue) is missing DWARF `DW_AT_location' for its `argc' and `argv' on 32-bit targets - only if these arguments are never unused. affected: x86_64-redhat-linux with -m32, i386-redhat-linux not affected: x86_64-redhat-linux (-m64) 32-bit broken for: gcc-4.1.1, SVN snapshot 4.3.0 always works: gcc-3.4.6 It causes gdb(1) to hide the arguments during backtrace: #0 main () at test.c:3 correct [i386]: echo 'int main (int argc, char **argv) { return argc + (int) argv; }' >main.c ;gcc -o main.o main.c -ggdb3;readelf -a --debug main.o|grep -A5 -w argc incorrect [i386]: echo 'int main (int argc, char **argv) { return 0; }' >main.c ;gcc -o main.o main.c -ggdb3;readelf -a --debug main.o|grep -A5 -w argc correct (gcc-3.4.6): <1><ee3>: Abbrev Number: 33 (DW_TAG_subprogram) DW_AT_sibling : <f63> DW_AT_external : 1 DW_AT_name : main DW_AT_decl_file : 46 DW_AT_decl_line : 267 DW_AT_prototyped : 1 DW_AT_type : <c4> DW_AT_low_pc : 0x8048c0f DW_AT_high_pc : 0x8048e26 DW_AT_frame_base : 616 (location list) <2><f02>: Abbrev Number: 34 (DW_TAG_formal_parameter) DW_AT_name : argc DW_AT_decl_file : 46 DW_AT_decl_line : 267 DW_AT_type : <c4> DW_AT_location : 2 byte block: 91 0 (DW_OP_fbreg: 0) <2><f12>: Abbrev Number: 34 (DW_TAG_formal_parameter) DW_AT_name : argv DW_AT_decl_file : 46 DW_AT_decl_line : 267 DW_AT_type : <f63> DW_AT_location : 2 byte block: 91 4 (DW_OP_fbreg: 4) incorrect (gcc-4.1.1; appropriately for SVN snapshot - ~4.3.0): <1><64>: Abbrev Number: 2 (DW_TAG_subprogram) DW_AT_external : 1 DW_AT_name : main DW_AT_decl_file : 1 DW_AT_decl_line : 2 DW_AT_prototyped : 1 DW_AT_type : <9b> DW_AT_low_pc : 0x8048324 DW_AT_high_pc : 0x804833d DW_AT_frame_base : 0 (location list) DW_AT_sibling : <9b> <2><82>: Abbrev Number: 3 (DW_TAG_formal_parameter) DW_AT_name : argc DW_AT_decl_file : 1 DW_AT_decl_line : 1 DW_AT_type : <9b> <2><8e>: Abbrev Number: 3 (DW_TAG_formal_parameter) DW_AT_name : argv DW_AT_decl_file : 1 DW_AT_decl_line : 1 DW_AT_type : <a2> dwarf2.out.c mem_loc_descriptor () GET_CODE (rtl): `case REG:' for i386 `argc'; it will fail on: if (REGNO (rtl) < FIRST_PSEUDO_REGISTER) Checked there: REGNO (rtl) == 61 /* Therefore pseudoreg. */ ORIGINAL_REGNO (rtl) == REGNO (rtl) reg_renumber [61] == -1 On i386 with the arguments used it is fine as: REGNO (rtl) == 1 /* Therefore hard register. */ On x86_64 it goes the `case PLUS:' way, not `case REG:'. Could you advice where to find the location information for pseudoregisters there?