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(gdb) added more information on syntax of formats and expressions

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scbj
2026-02-27 10:56:07 +01:00
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gdb.md
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@@ -21,7 +21,7 @@
| **command** | **description** |
|:----------------------|:--------------------------------------------------|
| `continue` | continue normal execution |
| `break <position>` | set breakpoint |
| `break <pos|exp>` | set breakpoint |
| `info breakpoint` | list breakpoints |
| `delete <#breakpoint>`| delete breakpoint |
| `step` | execute next instruction, then halt (step in) |
@@ -29,9 +29,10 @@
| `finish` | execute until the end of the current function (step out) |
| | |
| `backtrace` | show call stack |
| `print[/format]` | show content of variable/memory location/register |
| `x[/format] address` | print memory content at address |
| `list <position>` | show file/lines/symbol in source code window |
| `print[/fmt] exp` | show content of variable/memory location/register |
| `display[/fmt] exp` | print variable/memory on every program stop |
| `x[/fmt] address` | print memory content at address |
| `list <pos>` | show file/lines/symbol in source code window |
| | |
| `tui disable` | disable tui |
| `tui enable` | enable tui |
@@ -39,6 +40,9 @@
| `layout next/prev` | choose next or previous layout |
| `focus <window>` | focus specified window |
### position specifier
| **position** | **description** |
|:----------------------|:--------------------------------------------------|
| `<symbol-name>` | name of a symbol, e.g. function name |
@@ -46,6 +50,40 @@
| `<file>:<line>` | line number in the specified file |
### format specifier
`fmt = <count><format><unit>`
| **symbol** | **category** | **description** |
|:-----------|:------------:|:------------------------|
| `d` | format | decimal |
| `x` | format | hexadecimal |
| `o` | format | octal |
| `u` | format | unsigned decimal |
| `t` | format | binary |
| `f` | format | float |
| `a` | format | address |
| `i` | format | instruction |
| `c` | format | character |
| `s` | format | string |
| `z` | format | hexadecimal zero padded |
| | | |
| `b` | unit | byte |
| `h` | unit | halfword (2 bytes) |
| `w` | unit | word (4 bytes) |
| `g` | unit | giant (8 bytes) |
### notes on expressions (breakpoint/display/print)
In Assembly one can use `$<reg>` to target the value of a register.
To get the value of a variable or constant, use `&<symbol>`.
In higher level languages like C, prefixing a symbol with `&` get its address.
Local symbols are only valid in their scope and may not exist at all when
compiled with optimisations.
## reset program
To reset the program one can use the following command