Compilation with GCC 11 fails

[Vascom]

I can't build stlink 1.6.1 with GCC 11 compiler. Fedora GNU/Linux Rawhide.
Errors are:

/builddir/build/BUILD/stlink-1.6.1/src/st-util/gdb-server.c:90:22: error: 'stlink_open_usb' accessing 64 bytes in a region of size 28 [-Werror=stringop-overflow=]
   90 |                 sl = stlink_open_usb(st->logging_level, st->reset, serialnumber, 0);
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/builddir/build/BUILD/stlink-1.6.1/src/st-util/gdb-server.c: In function 'serve':
/builddir/build/BUILD/stlink-1.6.1/src/st-util/gdb-server.c:90:22: note: referencing argument 3 of type 'char *'
In file included from /builddir/build/BUILD/stlink-1.6.1/include/stlink.h:297,
                 from /builddir/build/BUILD/stlink-1.6.1/src/st-util/gdb-server.c:27:
/builddir/build/BUILD/stlink-1.6.1/src/usb.h:71:15: note: in a call to function 'stlink_open_usb'
   71 |     stlink_t *stlink_open_usb(enum ugly_loglevel verbose, int reset, char serial[STLINK_SERIAL_MAX_SIZE], int freq);
      |               ^~~~~~~~~~~~~~~

In function 'do_connect',
    inlined from 'do_connect' at /builddir/build/BUILD/stlink-1.6.1/src/st-util/gdb-server.c:87:18,
    inlined from 'main' at /builddir/build/BUILD/stlink-1.6.1/src/st-util/gdb-server.c:212:10:
/builddir/build/BUILD/stlink-1.6.1/src/st-util/gdb-server.c:90:22: error: 'stlink_open_usb' accessing 64 bytes in a region of size 28 [-Werror=stringop-overflow=]
   90 |                 sl = stlink_open_usb(st->logging_level, st->reset, serialnumber, 0);
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Please help me correct it.

[Vascom]

May be STLINK_SERIAL_MAX_SIZE define should be set to 28?

[Ant-ON]

You may fix src/st-util/gdb-server.c:

static char serialnumber[28] = {0};

to

static char serialnumber[STLINK_SERIAL_MAX_SIZE] = {0};

[Vascom]

I prefer see fix in upstream.

[Ant-ON]

@Vascom I too. But to fix it in upstream, you need to check works of it.

ps You have created a issue description not in accordance with a template. @Nightwalker-87 may delete it. See #906

[Vascom]

Yes, it works.

Template not care about compiling problems.

[Nightwalker-87]

The template is meant to be used and to be filled with content which also includes a description. So please consider this next time.

[JeffreyALaw]

You may fix src/st-util/gdb-server.c:

static char serialnumber[28] = {0};

to

static char serialnumber[STLINK_SERIAL_MAX_SIZE] = {0};

I nearly suggested that (I originally found the issue testing gcc-11 with Fedora). My concern with that was this loop in gdb-server.c:
for (size_t k = 0; j >= 0 && k < sizeof(serialnumber); ++k, j -= 2) {
char buffer[3] = {0};
memcpy(buffer, optarg + j, 2);
serialnumber[length - k] = (uint8_t)strtol(buffer, NULL, 16);

Which would be affected by changing the size of "serialnumber". Without knowing the intent or the code in general I didn't feel comfortable recommending changing the size of "serialnumber".

And to give folks a bit of background. gcc-11 has added diagnostics to detect out of bounds accesses for array arguments. In simplest terms if a function declares an argument as an array with a fixed length, then GCC assumes the entire array could potentially be referenced.

stlink_open_usb declares its 3rd argument as a 64 byte character array, yet "serialnumber" is just 28 bytes and GCC naturally warns because it thinks there's a potential out-of-bounds of the "serialnumber" argument by stlink_open_usb.