QTest::CrashHandler: move the Unix async-safe I/O code to the .cpp

This declutters the header from code that doesn't need to be there and
is only used in the .cpp anyway. This code used to be in qtestcase.cpp
before commit c0014becca2cd376eadd5c8a0265e5cf47c9aa01, which we now
amend. Additionally, since Windows code doesn't need to be async-safe
anyway, we can simplify it.

I'm also going to need the toHexString() lambda in another place.

Change-Id: Ic9571bac864dfb31564cfffd785e8ab15cab3ae5
Reviewed-by: Edward Welbourne <[email protected]>
Reviewed-by: Ahmad Samir <[email protected]>

1 files changed, 56 insertions, 11 deletions

diff --git a/src/testlib/qtestcrashhandler_unix.cpp b/src/testlib/qtestcrashhandler_unix.cpp
index f0ffe36dd66..86a77312ba4 100644
--- a/src/testlib/qtestcrashhandler_unix.cpp
+++ b/src/testlib/qtestcrashhandler_unix.cpp
@@ -68,21 +68,36 @@ QT_BEGIN_NAMESPACE
 
 using namespace Qt::StringLiterals;
 
-namespace QTest {
-namespace CrashHandler {
-struct iovec IoVec(struct iovec vec)
+template <typename... Args> static ssize_t writeToStderr(Args &&... args)
 {
-    return vec;
+    auto makeIovec = [](auto &&arg) {
+        if constexpr (std::is_same_v<std::decay_t<decltype(arg)>, iovec>) {
+            return arg;
+        } else {
+            struct iovec r = {};
+            r.iov_base = const_cast<char *>(arg);
+            r.iov_len = strlen(arg);
+            return r;
+        }
+    };
+    struct iovec vec[] = { makeIovec(std::forward<Args>(args))... };
+    return ::writev(STDERR_FILENO, vec, std::size(vec));
 }
-struct iovec IoVec(const char *str)
+
+namespace {
+// async-signal-safe conversion from int to string
+struct AsyncSafeIntBuffer
 {
-    struct iovec r = {};
-    r.iov_base = const_cast<char *>(str);
-    r.iov_len = strlen(str);
-    return r;
-}
+    // digits10 + 1 for all possible digits
+    // +1 for the sign
+    // +1 for the terminating null
+    static constexpr int Digits10 = std::numeric_limits<int>::digits10 + 3;
+    std::array<char, Digits10> array;
+    constexpr AsyncSafeIntBuffer() : array{} {}     // initializes array
+    AsyncSafeIntBuffer(Qt::Initialization) {}       // leaves array uninitialized
+};
 
-struct iovec asyncSafeToString(int n, AsyncSafeIntBuffer &&result)
+struct iovec asyncSafeToString(int n, AsyncSafeIntBuffer &&result = Qt::Uninitialized)
 {
     char *ptr = result.array.data();
     if (false) {
@@ -127,7 +142,10 @@ struct iovec asyncSafeToString(int n, AsyncSafeIntBuffer &&result)
     r.iov_len = ptr - result.array.data();
     return r;
 };
+} // unnamed namespace
 
+namespace QTest {
+namespace CrashHandler {
 bool alreadyDebugging()
 {
 #if defined(Q_OS_LINUX)
@@ -349,6 +367,33 @@ void blockUnixSignals()
     pthread_sigmask(SIG_BLOCK, &set, nullptr);
 }
 
+template <typename T> static
+        std::enable_if_t<sizeof(std::declval<T>().si_pid) + sizeof(std::declval<T>().si_uid) >= 1>
+printSentSignalInfo(T *info)
+{
+    writeToStderr(" sent by PID ", asyncSafeToString(info->si_pid),
+                  " UID ", asyncSafeToString(info->si_uid));
+}
+[[maybe_unused]] static void printSentSignalInfo(...) {}
+
+template <typename T> static std::enable_if_t<sizeof(std::declval<T>().si_addr) >= 1>
+printCrashingSignalInfo(T *info)
+{
+    using HexString = std::array<char, sizeof(quintptr) * 2>;
+    auto toHexString = [](quintptr u, HexString &&r = {}) {
+        int shift = sizeof(quintptr) * 8 - 4;
+        for (size_t i = 0; i < sizeof(quintptr) * 2; ++i, shift -= 4)
+            r[i] = QtMiscUtils::toHexLower(u >> shift);
+        struct iovec vec;
+        vec.iov_base = r.data();
+        vec.iov_len = r.size();
+        return vec;
+    };
+    writeToStderr(", code ", asyncSafeToString(info->si_code),
+                  ", for address 0x", toHexString(quintptr(info->si_addr)));
+}
+[[maybe_unused]] static void printCrashingSignalInfo(...) {}
+
 bool FatalSignalHandler::pauseOnCrash = false;
 
 FatalSignalHandler::FatalSignalHandler()