AVR - invalid address used when evaluating a variable
Christo <[email protected]>
| Newsgroups | gmane.comp.gdb.devel |
|---|---|
| Message-ID | <[email protected]> |
I am testing the debugging of AVR microcontrollers over debugWIRE with gdb. When evaluating the value of a variable I noticed an incorrect value. On closer inspection I realized that gdb (8.1 compiled for AVR support) was reading flash memory, not SRAM. When I evaluate the pointer to the variable, gdb correctly reports the SRAM address. When reading the memory pointed to by this pointer the correct value is returned. This leads me to postulate that there is a mistake/omission when gdb evaluates/prints a variable, resolve its address and then reads it from flash rather than SRAM. Below a short excerpt of debugging a simple program with a variable "i" which the compiler located at address 0 in SRAM (which should be mapped to 0x800060, right after the io registers). The program was compiled with Freepascal and debugged using a debugWIRE server. I've called "set debug remote 1" so that the rsp requests can be seen: (gdb) print i Sending packet: $m60,1#30...Ack Packet received: 20 $7 = 32 ' ' (gdb) print &i $8 = (Byte *) 0x800060 <TC_sPsBLINK_ss_I> Sending packet: $m800060,8#ff...Ack Packet received: 020003B8F6777DD2 "\002" (gdb) print *&i Sending packet: $m800060,1#f8...Ack Packet received: 02 $9 = 2 '\002' Can anyone confirm this behaviour is indeed wrong/unexpected?