[fpc-devel] Incorrect debug info for ESP32, linker error?

[Christo Crause]

On Sat, Dec 4, 2021 at 5:23 PM Florian Klämpfl via fpc-devel <
fpc-devel at lists.freepascal.org> wrote:

> Am 04.12.2021 um 14:04 schrieb Christo Crause via fpc-devel:
> > When compiling a simple test for esp32 (xtensa-freertos), the incorrect
> values for DW_AT_low_PC and DW_AT_high_PC are
> > generated.  From my inspection of the generated assembler I cannot see
> anything wrong, but the values supplied by the
> > linker are wrong.  Any ideas on how to fix this?
> >
> > This can be seen below, where there is no overlap between the unit's
> low/high PC and main's low/high PC:
> >
> >   <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
> >      <c>   DW_AT_name        : test.pp
> >      <14>   DW_AT_producer    : Free Pascal 3.3.1 2021/11/27
> >      <31>   DW_AT_comp_dir    : /home/christo/fpc/xtensa/examples/test/
> >      <59>   DW_AT_language    : 9 (ANSI Pascal)
> >      <5a>   DW_AT_identifier_case: 3 (case_insensitive)
> >      <5b>   DW_AT_stmt_list   : 0x0
> >      <5f>   DW_AT_low_pc      : 0x400e49e4
> >      <63>   DW_AT_high_pc     : 0x400e49e4
> >   <1><67>: Abbrev Number: 2 (DW_TAG_subprogram)
> >      <68>   DW_AT_name        : $main
> >      <6e>   DW_AT_prototyped  : 1
> >      <6f>   DW_AT_external    : 1
> >      <70>   DW_AT_low_pc      : 0x400d0a70
> >      <74>   DW_AT_high_pc     : 0x400d0ab3
> >
> >  From the compiler generated assembly it appears that the labels for
> these values are correctly placed
> > (DEBUGSTART_$P$TEST placed at start of code):
> >
> > .globl DEBUGSTART_$P$TEST
> > DEBUGSTART_$P$TEST:
> > # End asmlist al_begin
> > # Begin asmlist al_procedures
> >
> > .section .text.n_main,"ax"
> > .balign 4
> > .globl main
> > main:
> > .globl PASCALMAIN
> > PASCALMAIN:
> > .Lc2:
> > #   Start of abi_windowed entry localsize=0
> >
> > Below the label is used in the debug info section:
> >
> > .section .debug_info
> > .Ldebug_info0:
> > .long .Ledebug_info0-.Lf2
> > .Lf2:
> > .short 3
> > .long .Ldebug_abbrev0
> > .byte 4
> > .uleb128 1
> > .ascii "test.pp\000"
> > .ascii "Free Pascal 3.3.1 2021/11/27\000"
> > .ascii "/home/christo/fpc/xtensa/examples/test/\000"
> > .byte 9
> > .byte 3
> > .long .Ldebug_line0
> > .long DEBUGSTART_$P$TEST
> > .long DEBUGEND_$P$TEST
>
> How does the debug info section look like for a gcc generated program?
>

The debug info for the main file in the project (other file information
looks similar):

  Compilation Unit @ offset 0xf7476:
   Length:        0x6347 (32-bit)
   Version:       4
   Abbrev Offset: 0xe85d
   Pointer Size:  4
 <0><f7481>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <f7482>   DW_AT_producer    : (indirect string, offset: 0xa4): GNU C99
8.4.0 -mlongcalls -ggdb -Og -std=gnu99 -ffunction-sections -fdata-sections
-fstrict-volatile-bitfields
    <f7486>   DW_AT_language    : 12 (ANSI C99)
    <f7487>   DW_AT_name        : (indirect string, offset: 0x14b84):
../main/sd_card_example_main.c
    <f748b>   DW_AT_comp_dir    : (indirect string, offset: 0x689):
/home/christo/xtensa/examples/sd_card/build
    <f748f>   DW_AT_ranges      : 0x3148
    <f7493>   DW_AT_low_pc      : 0x0
    <f7497>   DW_AT_stmt_list   : 0x59c73
 <1><f749b>: Abbrev Number: 2 (DW_TAG_base_type)
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