linux_core_dumper: add explicit casts for exception fields

Some of the fields we save might have signed types depending on the
system (e.g. `typedef int pid_t`).  Depending on the toolchain, we
can trip -Werror=narrowing failures like:
src/client/linux/minidump_writer/linux_core_dumper.cc:248:66: error:
  narrowing conversion of ‘(__pid_t)info->siginfo_t::_sifields.siginfo_t::<anonymous union>::_kill.siginfo_t::<anonymous union>::<anonymous struct>::si_pid’
  from ‘__pid_t {aka int}’ to ‘long unsigned int’ inside { } [-Werror=narrowing]
             set_crash_exception_info({info->si_pid, info->si_uid});
                                             ^^^^^^
src/client/linux/minidump_writer/linux_core_dumper.cc:252:71: error:
  narrowing conversion of ‘(int)info->siginfo_t::_sifields.siginfo_t::<anonymous union>::_sigsys.siginfo_t::<anonymous union>::<anonymous struct>::_syscall’
  from ‘int’ to ‘long unsigned int’ inside { } [-Werror=narrowing]
             set_crash_exception_info({info->si_syscall, info->si_arch});
                                             ^^^^^^^^^^

Since the exception info fields are all uint64_t which should be large
enough to handle all the fields in the siginfo_t structure, add casts
for all the assignments to avoid these errors.  We have implicit casts
even without them, so we aren't changing behavior.

Bug: google-breakpad:791
Bug: chromium:945653
Change-Id: Ib04e015998f08b857159ac13e9a065a66d228d49
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/1544862
Reviewed-by: Mark Mentovai <mark@chromium.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/src/client/linux/minidump_writer/linux_core_dumper.cc b/src/client/linux/minidump_writer/linux_core_dumper.cc
index 3b1eabb4..41506898 100644
--- a/src/client/linux/minidump_writer/linux_core_dumper.cc
+++ b/src/client/linux/minidump_writer/linux_core_dumper.cc
@@ -242,14 +242,21 @@ bool LinuxCoreDumper::EnumerateThreads() {
             break;
         }
 
-        // Set crash_exception_info for common signals.
+        // Set crash_exception_info for common signals.  Since exception info is
+        // unsigned, but some of these fields might be signed, we always cast.
         switch (info->si_signo) {
           case MD_EXCEPTION_CODE_LIN_SIGKILL:
-            set_crash_exception_info({info->si_pid, info->si_uid});
+            set_crash_exception_info({
+              static_cast<uint64_t>(info->si_pid),
+              static_cast<uint64_t>(info->si_uid),
+            });
             break;
           case MD_EXCEPTION_CODE_LIN_SIGSYS:
 #ifdef si_syscall
-            set_crash_exception_info({info->si_syscall, info->si_arch});
+            set_crash_exception_info({
+              static_cast<uint64_t>(info->si_syscall),
+              static_cast<uint64_t>(info->si_arch),
+            });
 #endif
             break;
         }