Fix a possible integer overflow

[mmisono]

When I tried to use UndefinedSanitizer (by
CXXFLAGS="-fsanitize=undefined"), I found the following error.

% sudo ./src/bpftrace -e 'BEGIN{curtask}'
/home/ubuntu/work/bpftrace_master/src/clang_parser.cpp:225:22: runtime error: shift exponent 64 is too large for 32-bit type 'int'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/ubuntu/work/bpftrace_master/src/clang_parser.cpp:225:22 in
/home/ubuntu/work/bpftrace_master/src/clang_parser.cpp:225:44: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/ubuntu/work/bpftrace_master/src/clang_parser.cpp:225:44 in

It warned about integer overflows. This patch fixes this.

Checklist

• Language changes are updated in docs/reference_guide.md
• User-visible and non-trivial changes updated in CHANGELOG.md
• The new behaviour is covered by tests

[fbs]

Shouldn't this be >=32 as the warning is:

shift exponent 64 is too large for 32-bit type 'int'

[fbs]

of maybe

if (width >= sizeof(size_t)) {
  mask = SSIZE_MAX
}

[mmisono]

Shouldn't this be >=32 as the warning is:

Isn't bitfield_bitwidth >= 32 possible? something like struct {long x: 48; long y: 16}

of maybe

if (width >= sizeof(size_t)) {
  mask = SSIZE_MAX
}

ah, this seems better. will fix.

[fbs]

Shouldn't we make bitfield.mask an uint64_t then, to avoid issues on 32bit?

[mmisono]

It makes sense. I also noticed that both clang and gcc support __int128. So I added the support of it.

[mmisono]

I realized that bpftrace does not support __int128. So, change it to use uint64_t

[mmisono]

hmm.. it seems the error reason for the embedded build is not related to this.

/home/runner/work/bpftrace/bpftrace/src/attached_probe.cpp: In member function 'void bpftrace::AttachedProbe::attach_uprobe(bool)':
/home/runner/work/bpftrace/bpftrace/src/attached_probe.cpp:706:51: error: too few arguments to function 'int bpf_attach_uprobe(int, bpf_probe_attach_type, const char*, const char*, uint64_t, pid_t, uint32_t)'
                                         probe_.pid);
                                                   ^
[...]
```