Creating debug symbols for gdb manually
1
Intro. For my compilers course I have to translate some language to assembler. Now my code has a segfault, and I have hard time debugging it. Having an ability to watch variables would simplify the process a lot, but the final asm code has only registers and their derivatives.
Question. How can I create debug symbols for gdb manually? I believe I can propagate all necessary information. Will the separate file be created or will it be part of asm? In the former case how to make gdb aware of that file?
A link to some manual is enough. I've searched for one and was only able to find "gcc -g" and some questions about generating symbol files separately.
assembly compiler-construction gdb debug-symbols
asked Nov 10 at 19:29
dyukha
31618
|
show 1 more comment
1
Intro. For my compilers course I have to translate some language to assembler. Now my code has a segfault, and I have hard time debugging it. Having an ability to watch variables would simplify the process a lot, but the final asm code has only registers and their derivatives.
Question. How can I create debug symbols for gdb manually? I believe I can propagate all necessary information. Will the separate file be created or will it be part of asm? In the former case how to make gdb aware of that file?
A link to some manual is enough. I've searched for one and was only able to find "gcc -g" and some questions about generating symbol files separately.
assembly compiler-construction gdb debug-symbols
asked Nov 10 at 19:29
dyukha
31618
2
It's normally part of the asm, with special directives to emit a section of debug info. Look at the output ofgcc -Son a.cfile, with and without-g. e.g. have a look at the stuff after the.section .debug_info,"",@progbitsdirective in godbolt.org/z/EdeTvA. (gcc compiling for Linux/ELF MIPS). What target are you compiling for, BTW? Different debug formats exist, with DWARF being the current widely-used on on Linux/ELF targets.
– Peter Cordes
Nov 10 at 19:34
@PeterCordes, thank you. I understand now that it's part of asm. I guess I have to read about .loc and stuff: stackoverflow.com/a/30212164/2956272. My gcc compiler is x86-64 gcc 7.3.
– dyukha
Nov 10 at 19:45
2
Yup. Or maybe just have your compiler emit comments on the asm source lines, like gcc's-fverbose-asmdoes (try adding it on the Godbolt link above), and assemble it with an assembler that generates debug info for asm source-level debugging. (likeas -g). So you give yourself some way to single-step the asm and see some strings from your compiler attached to each instruction, naming the operands. Doesn't help so much for setting watchpoints, but can help follow the how the compiler is implementing the source logic.
– Peter Cordes
Nov 10 at 19:49
@PeterCordes, Can you please clarify a bit more? I can see lines like this:mov rdx, QWORD PTR [rbp-8] # tmp89, a. Do I understand correctly that compiler now knows thatrdxistmp89andQWORD PTR [rbp-8]isajust from that? Willgcc -g <my-asm>compilation do it? If yes, this may be exactly what I need.
– dyukha
Nov 10 at 20:02
1
Yes, the comments just repeat the operand list using C variable names, or variations ontmpXXfor internal temporaries. And yeah, I thinkgcc -g foo.swill give you the debug info to help GDB show the right asm source lines.
– Peter Cordes
Nov 10 at 20:12
|
show 1 more comment
1
1
1
Intro. For my compilers course I have to translate some language to assembler. Now my code has a segfault, and I have hard time debugging it. Having an ability to watch variables would simplify the process a lot, but the final asm code has only registers and their derivatives.
Question. How can I create debug symbols for gdb manually? I believe I can propagate all necessary information. Will the separate file be created or will it be part of asm? In the former case how to make gdb aware of that file?
A link to some manual is enough. I've searched for one and was only able to find "gcc -g" and some questions about generating symbol files separately.
assembly compiler-construction gdb debug-symbols
asked Nov 10 at 19:29
dyukha
31618
Intro. For my compilers course I have to translate some language to assembler. Now my code has a segfault, and I have hard time debugging it. Having an ability to watch variables would simplify the process a lot, but the final asm code has only registers and their derivatives.
Question. How can I create debug symbols for gdb manually? I believe I can propagate all necessary information. Will the separate file be created or will it be part of asm? In the former case how to make gdb aware of that file?
A link to some manual is enough. I've searched for one and was only able to find "gcc -g" and some questions about generating symbol files separately.
assembly compiler-construction gdb debug-symbols
assembly compiler-construction gdb debug-symbols
asked Nov 10 at 19:29
dyukha
31618
asked Nov 10 at 19:29
dyukha
31618
edited Nov 10 at 19:31
asked Nov 10 at 19:29
dyukha
31618
asked Nov 10 at 19:29
dyukha
31618
asked Nov 10 at 19:29
dyukha
31618
31618
2
It's normally part of the asm, with special directives to emit a section of debug info. Look at the output ofgcc -Son a.cfile, with and without-g. e.g. have a look at the stuff after the.section .debug_info,"",@progbitsdirective in godbolt.org/z/EdeTvA. (gcc compiling for Linux/ELF MIPS). What target are you compiling for, BTW? Different debug formats exist, with DWARF being the current widely-used on on Linux/ELF targets.
– Peter Cordes
Nov 10 at 19:34
@PeterCordes, thank you. I understand now that it's part of asm. I guess I have to read about .loc and stuff: stackoverflow.com/a/30212164/2956272. My gcc compiler is x86-64 gcc 7.3.
– dyukha
Nov 10 at 19:45
2
Yup. Or maybe just have your compiler emit comments on the asm source lines, like gcc's-fverbose-asmdoes (try adding it on the Godbolt link above), and assemble it with an assembler that generates debug info for asm source-level debugging. (likeas -g). So you give yourself some way to single-step the asm and see some strings from your compiler attached to each instruction, naming the operands. Doesn't help so much for setting watchpoints, but can help follow the how the compiler is implementing the source logic.
– Peter Cordes
Nov 10 at 19:49
@PeterCordes, Can you please clarify a bit more? I can see lines like this:mov rdx, QWORD PTR [rbp-8] # tmp89, a. Do I understand correctly that compiler now knows thatrdxistmp89andQWORD PTR [rbp-8]isajust from that? Willgcc -g <my-asm>compilation do it? If yes, this may be exactly what I need.
– dyukha
Nov 10 at 20:02
1
Yes, the comments just repeat the operand list using C variable names, or variations ontmpXXfor internal temporaries. And yeah, I thinkgcc -g foo.swill give you the debug info to help GDB show the right asm source lines.
– Peter Cordes
Nov 10 at 20:12
|
show 1 more comment
2
It's normally part of the asm, with special directives to emit a section of debug info. Look at the output ofgcc -Son a.cfile, with and without-g. e.g. have a look at the stuff after the.section .debug_info,"",@progbitsdirective in godbolt.org/z/EdeTvA. (gcc compiling for Linux/ELF MIPS). What target are you compiling for, BTW? Different debug formats exist, with DWARF being the current widely-used on on Linux/ELF targets.
– Peter Cordes
Nov 10 at 19:34
@PeterCordes, thank you. I understand now that it's part of asm. I guess I have to read about .loc and stuff: stackoverflow.com/a/30212164/2956272. My gcc compiler is x86-64 gcc 7.3.
– dyukha
Nov 10 at 19:45
2
Yup. Or maybe just have your compiler emit comments on the asm source lines, like gcc's-fverbose-asmdoes (try adding it on the Godbolt link above), and assemble it with an assembler that generates debug info for asm source-level debugging. (likeas -g). So you give yourself some way to single-step the asm and see some strings from your compiler attached to each instruction, naming the operands. Doesn't help so much for setting watchpoints, but can help follow the how the compiler is implementing the source logic.
– Peter Cordes
Nov 10 at 19:49
@PeterCordes, Can you please clarify a bit more? I can see lines like this:mov rdx, QWORD PTR [rbp-8] # tmp89, a. Do I understand correctly that compiler now knows thatrdxistmp89andQWORD PTR [rbp-8]isajust from that? Willgcc -g <my-asm>compilation do it? If yes, this may be exactly what I need.
– dyukha
Nov 10 at 20:02
1
Yes, the comments just repeat the operand list using C variable names, or variations ontmpXXfor internal temporaries. And yeah, I thinkgcc -g foo.swill give you the debug info to help GDB show the right asm source lines.
– Peter Cordes
Nov 10 at 20:12
2
2
It's normally part of the asm, with special directives to emit a section of debug info. Look at the output of
gcc -S on a .c file, with and without -g. e.g. have a look at the stuff after the .section .debug_info,"",@progbits directive in godbolt.org/z/EdeTvA. (gcc compiling for Linux/ELF MIPS). What target are you compiling for, BTW? Different debug formats exist, with DWARF being the current widely-used on on Linux/ELF targets.– Peter Cordes
Nov 10 at 19:34
It's normally part of the asm, with special directives to emit a section of debug info. Look at the output of
gcc -S on a .c file, with and without -g. e.g. have a look at the stuff after the .section .debug_info,"",@progbits directive in godbolt.org/z/EdeTvA. (gcc compiling for Linux/ELF MIPS). What target are you compiling for, BTW? Different debug formats exist, with DWARF being the current widely-used on on Linux/ELF targets.– Peter Cordes
Nov 10 at 19:34
@PeterCordes, thank you. I understand now that it's part of asm. I guess I have to read about .loc and stuff: stackoverflow.com/a/30212164/2956272. My gcc compiler is x86-64 gcc 7.3.
– dyukha
Nov 10 at 19:45
@PeterCordes, thank you. I understand now that it's part of asm. I guess I have to read about .loc and stuff: stackoverflow.com/a/30212164/2956272. My gcc compiler is x86-64 gcc 7.3.
– dyukha
Nov 10 at 19:45
2
2
Yup. Or maybe just have your compiler emit comments on the asm source lines, like gcc's
-fverbose-asm does (try adding it on the Godbolt link above), and assemble it with an assembler that generates debug info for asm source-level debugging. (like as -g). So you give yourself some way to single-step the asm and see some strings from your compiler attached to each instruction, naming the operands. Doesn't help so much for setting watchpoints, but can help follow the how the compiler is implementing the source logic.– Peter Cordes
Nov 10 at 19:49
Yup. Or maybe just have your compiler emit comments on the asm source lines, like gcc's
-fverbose-asm does (try adding it on the Godbolt link above), and assemble it with an assembler that generates debug info for asm source-level debugging. (like as -g). So you give yourself some way to single-step the asm and see some strings from your compiler attached to each instruction, naming the operands. Doesn't help so much for setting watchpoints, but can help follow the how the compiler is implementing the source logic.– Peter Cordes
Nov 10 at 19:49
@PeterCordes, Can you please clarify a bit more? I can see lines like this:
mov rdx, QWORD PTR [rbp-8] # tmp89, a. Do I understand correctly that compiler now knows that rdx is tmp89 and QWORD PTR [rbp-8] is a just from that? Will gcc -g <my-asm> compilation do it? If yes, this may be exactly what I need.– dyukha
Nov 10 at 20:02
@PeterCordes, Can you please clarify a bit more? I can see lines like this:
mov rdx, QWORD PTR [rbp-8] # tmp89, a. Do I understand correctly that compiler now knows that rdx is tmp89 and QWORD PTR [rbp-8] is a just from that? Will gcc -g <my-asm> compilation do it? If yes, this may be exactly what I need.– dyukha
Nov 10 at 20:02
1
1
Yes, the comments just repeat the operand list using C variable names, or variations on
tmpXX for internal temporaries. And yeah, I think gcc -g foo.s will give you the debug info to help GDB show the right asm source lines.– Peter Cordes
Nov 10 at 20:12
Yes, the comments just repeat the operand list using C variable names, or variations on
tmpXX for internal temporaries. And yeah, I think gcc -g foo.s will give you the debug info to help GDB show the right asm source lines.– Peter Cordes
Nov 10 at 20:12
|
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2
It's normally part of the asm, with special directives to emit a section of debug info. Look at the output of
gcc -Son a.cfile, with and without-g. e.g. have a look at the stuff after the.section .debug_info,"",@progbitsdirective in godbolt.org/z/EdeTvA. (gcc compiling for Linux/ELF MIPS). What target are you compiling for, BTW? Different debug formats exist, with DWARF being the current widely-used on on Linux/ELF targets.– Peter Cordes
Nov 10 at 19:34
@PeterCordes, thank you. I understand now that it's part of asm. I guess I have to read about .loc and stuff: stackoverflow.com/a/30212164/2956272. My gcc compiler is x86-64 gcc 7.3.
– dyukha
Nov 10 at 19:45
2
Yup. Or maybe just have your compiler emit comments on the asm source lines, like gcc's
-fverbose-asmdoes (try adding it on the Godbolt link above), and assemble it with an assembler that generates debug info for asm source-level debugging. (likeas -g). So you give yourself some way to single-step the asm and see some strings from your compiler attached to each instruction, naming the operands. Doesn't help so much for setting watchpoints, but can help follow the how the compiler is implementing the source logic.– Peter Cordes
Nov 10 at 19:49
@PeterCordes, Can you please clarify a bit more? I can see lines like this:
mov rdx, QWORD PTR [rbp-8] # tmp89, a. Do I understand correctly that compiler now knows thatrdxistmp89andQWORD PTR [rbp-8]isajust from that? Willgcc -g <my-asm>compilation do it? If yes, this may be exactly what I need.– dyukha
Nov 10 at 20:02
1
Yes, the comments just repeat the operand list using C variable names, or variations on
tmpXXfor internal temporaries. And yeah, I thinkgcc -g foo.swill give you the debug info to help GDB show the right asm source lines.– Peter Cordes
Nov 10 at 20:12