Repository: bitcoin/bitcoin
File: src/util/threadnames.cpp (C++)

Code before:
//! Set the thread's name at the process level. Does not affect the
//! internal name.
static void SetThreadName(const char* name)
{
#if defined(PR_SET_NAME)
    // Only the first 15 characters are used (16 - NUL terminator)
    ::prctl(PR_SET_NAME, name, 0, 0, 0);
#elif (defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__))
    pthread_set_name_np(pthread_self(), name);
#elif defined(MAC_OSX)
    pthread_setname_np(name);
#else
    // Prevent warnings for unused parameters...
    (void)name;
#endif
}

// If we have thread_local, just keep thread ID and name in a thread_local
// global.
#if defined(HAVE_THREAD_LOCAL)

static thread_local std::string g_thread_name;
const std::string& util::ThreadGetInternalName() { return g_thread_name; }
//! Set the in-memory internal name for this thread. Does not affect the process
//! name.
static void SetInternalName(std::string name) { g_thread_name = std::move(name); }

// Without thread_local available, don't handle internal name at all.
#else

static const std::string empty_string;
const std::string& util::ThreadGetInternalName() { return empty_string; }
static void SetInternalName(std::string name) { }
#endif

void util::ThreadRename(std::string&& name)
{
    SetThreadName(("b-" + name).c_str());
    SetInternalName(std::move(name));
}

void util::ThreadSetInternalName(std::string&& name)
{
    SetInternalName(std::move(name));
}


Review comment (suggestion):
If we are outlawing thread_local usage, then at the same time, this commit should remove other comments from our codebase suggesting further thread_local usage. i.e [ * If thread-safety is needed, the global could be made thread_local (given](https://github.com/bitcoin/bitcoin/blob/058af75874ffa2b4064e3d6d30cc50f0ec754ba8/src/test/util/random.h#L17)

Code after:

//! Set the thread's name at the process level. Does not affect the
//! internal name.
static void SetThreadName(const char* name)
{
#if defined(PR_SET_NAME)
    // Only the first 15 characters are used (16 - NUL terminator)
    ::prctl(PR_SET_NAME, name, 0, 0, 0);
#elif (defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__))
    pthread_set_name_np(pthread_self(), name);
#elif defined(MAC_OSX)
    pthread_setname_np(name);
#else
    // Prevent warnings for unused parameters...
    (void)name;
#endif
}

// If we have thread_local, just keep thread ID and name in a thread_local
// global.
#if defined(HAVE_THREAD_LOCAL)

/**
 * The name of the thread. We use char array instead of std::string to avoid
 * complications with running a destructor when the thread exits. Avoid adding
 * other thread_local variables.
 * @see https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=278701
 */
static thread_local char g_thread_name[128]{'\0'};
std::string util::ThreadGetInternalName() { return g_thread_name; }
//! Set the in-memory internal name for this thread. Does not affect the process
//! name.
static void SetInternalName(const std::string& name)
{
    const size_t copy_bytes{std::min(sizeof(g_thread_name) - 1, name.length())};
    std::memcpy(g_thread_name, name.data(), copy_bytes);
    g_thread_name[copy_bytes] = '\0';
}

// Without thread_local available, don't handle internal name at all.
#else

std::string util::ThreadGetInternalName() { return ""; }
static void SetInternalName(const std::string& name) { }
#endif

void util::ThreadRename(const std::string& name)
{
    SetThreadName(("b-" + name).c_str());
    SetInternalName(name);
}