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authorGravatar Abseil Team <absl-team@google.com>2019-10-21 10:21:03 -0700
committerGravatar Derek Mauro <dmauro@google.com>2019-10-21 14:35:27 -0400
commit2796d500aea5a31d26b8b24a33fab7a1c8fa2f32 (patch)
tree5c4ab36c15a95b8018038e28c124349efdcd6ba6 /absl/flags/internal/flag.cc
parente4c8d0eb8ef4acb5d7a4252b3b87feb391ef7e41 (diff)
Export of internal Abseil changes
-- b770d03c2f1042d399c3f9576e881691cbe962c4 by Abseil Team <absl-team@google.com>: Avoid applying the workaround for MSVC's static initialization problems when using clang-cl. PiperOrigin-RevId: 275870089 -- 2b8fc02ec49aeb5ad56cef20259cdd7f6ee0c917 by Abseil Team <absl-team@google.com>: Document return values. PiperOrigin-RevId: 275839042 -- baa99064f9a28b188661df7fba989fcd558818af by Abseil Team <absl-team@google.com>: Support "auto" and other uncommon builtin types in absl::debugging_internal::Demangle. PiperOrigin-RevId: 275556195 -- f9d5c6a3a0d374dbf105d6e2e9e0c8fa949ed187 by Gennadiy Rozental <rogeeff@google.com>: Internal rework. PiperOrigin-RevId: 275550005 -- 2679a77db5b26349e8c8b2059621af55d2fca139 by Mark Barolak <mbar@google.com>: Remove a comment reference to the no longer extant ::string implementation. PiperOrigin-RevId: 275531987 -- 7b427a7613c44a98c6f13da43b2bff2837ca6b19 by Derek Mauro <dmauro@google.com>: Upgrade to Bazel 1.0.0 and CMake 3.15.4 PiperOrigin-RevId: 275500823 -- 81f7d20905debf9d1e300bd2e9899f88d27f632a by Derek Mauro <dmauro@google.com>: Fix -Wimplicit-int-float-conversion warning in latest clang PiperOrigin-RevId: 275492439 GitOrigin-RevId: b770d03c2f1042d399c3f9576e881691cbe962c4 Change-Id: I9b39dad524489f0d62c912d02e8ac43761c81e55
Diffstat (limited to 'absl/flags/internal/flag.cc')
-rw-r--r--absl/flags/internal/flag.cc337
1 files changed, 316 insertions, 21 deletions
diff --git a/absl/flags/internal/flag.cc b/absl/flags/internal/flag.cc
index 0f403581..061113d7 100644
--- a/absl/flags/internal/flag.cc
+++ b/absl/flags/internal/flag.cc
@@ -15,36 +15,331 @@
#include "absl/flags/internal/flag.h"
+#include "absl/base/optimization.h"
#include "absl/synchronization/mutex.h"
namespace absl {
namespace flags_internal {
+namespace {
-// If the flag has a mutation callback this function invokes it. While the
-// callback is being invoked the primary flag's mutex is unlocked and it is
-// re-locked back after call to callback is completed. Callback invocation is
-// guarded by flag's secondary mutex instead which prevents concurrent
-// callback invocation. Note that it is possible for other thread to grab the
-// primary lock and update flag's value at any time during the callback
-// invocation. This is by design. Callback can get a value of the flag if
-// necessary, but it might be different from the value initiated the callback
-// and it also can be different by the time the callback invocation is
-// completed. Requires that *primary_lock be held in exclusive mode; it may be
-// released and reacquired by the implementation.
-void InvokeCallback(absl::Mutex* primary_mu, absl::Mutex* callback_mu,
- FlagCallback cb) ABSL_EXCLUSIVE_LOCKS_REQUIRED(primary_mu) {
- if (!cb) return;
-
- // When executing the callback we need the primary flag's mutex to be
- // unlocked so that callback can retrieve the flag's value.
- primary_mu->Unlock();
+// Currently we only validate flag values for user-defined flag types.
+bool ShouldValidateFlagValue(const CommandLineFlag& flag) {
+#define DONT_VALIDATE(T) \
+ if (flag.IsOfType<T>()) return false;
+ ABSL_FLAGS_INTERNAL_FOR_EACH_LOCK_FREE(DONT_VALIDATE)
+ DONT_VALIDATE(std::string)
+ DONT_VALIDATE(std::vector<std::string>)
+#undef DONT_VALIDATE
+ return true;
+}
+
+} // namespace
+
+void FlagImpl::Init() {
+ ABSL_CONST_INIT static absl::Mutex init_lock(absl::kConstInit);
+
+ {
+ absl::MutexLock lock(&init_lock);
+
+ if (locks_ == nullptr) { // Must initialize Mutexes for this flag.
+ locks_ = new FlagImpl::CommandLineFlagLocks;
+ }
+ }
+
+ absl::MutexLock lock(&locks_->primary_mu);
+
+ if (def_ != nullptr) {
+ inited_.store(true, std::memory_order_release);
+ } else {
+ // Need to initialize def and cur fields.
+ def_ = (*initial_value_gen_)();
+ cur_ = Clone(op_, def_);
+ StoreAtomic();
+ inited_.store(true, std::memory_order_release);
+ InvokeCallback();
+ }
+}
+
+// Ensures that the lazily initialized data is initialized,
+// and returns pointer to the mutex guarding flags data.
+absl::Mutex* FlagImpl::DataGuard() const
+ ABSL_LOCK_RETURNED(locks_->primary_mu) {
+ if (ABSL_PREDICT_FALSE(!inited_.load(std::memory_order_acquire))) {
+ const_cast<FlagImpl*>(this)->Init();
+ }
+
+ // All fields initialized; locks_ is therefore safe to read.
+ return &locks_->primary_mu;
+}
+
+void FlagImpl::Destroy() const {
{
- absl::MutexLock lock(callback_mu);
- cb();
+ absl::MutexLock l(DataGuard());
+
+ // Values are heap allocated for Abseil Flags.
+ if (cur_) Delete(op_, cur_);
+ if (def_) Delete(op_, def_);
}
- primary_mu->Lock();
+ delete locks_;
+}
+
+bool FlagImpl::IsModified() const {
+ absl::MutexLock l(DataGuard());
+ return modified_;
+}
+
+bool FlagImpl::IsSpecifiedOnCommandLine() const {
+ absl::MutexLock l(DataGuard());
+ return on_command_line_;
+}
+
+std::string FlagImpl::DefaultValue() const {
+ absl::MutexLock l(DataGuard());
+
+ return Unparse(marshalling_op_, def_);
+}
+
+std::string FlagImpl::CurrentValue() const {
+ absl::MutexLock l(DataGuard());
+
+ return Unparse(marshalling_op_, cur_);
+}
+
+void FlagImpl::SetCallback(
+ const flags_internal::FlagCallback mutation_callback) {
+ absl::MutexLock l(DataGuard());
+
+ callback_ = mutation_callback;
+
+ InvokeCallback();
+}
+
+void FlagImpl::InvokeCallback() const
+ ABSL_EXCLUSIVE_LOCKS_REQUIRED(locks_->primary_mu) {
+ if (!callback_) return;
+
+ // If the flag has a mutation callback this function invokes it. While the
+ // callback is being invoked the primary flag's mutex is unlocked and it is
+ // re-locked back after call to callback is completed. Callback invocation is
+ // guarded by flag's secondary mutex instead which prevents concurrent
+ // callback invocation. Note that it is possible for other thread to grab the
+ // primary lock and update flag's value at any time during the callback
+ // invocation. This is by design. Callback can get a value of the flag if
+ // necessary, but it might be different from the value initiated the callback
+ // and it also can be different by the time the callback invocation is
+ // completed. Requires that *primary_lock be held in exclusive mode; it may be
+ // released and reacquired by the implementation.
+ DataGuard()->Unlock();
+
+ {
+ absl::MutexLock lock(&locks_->callback_mu);
+ callback_();
+ }
+
+ DataGuard()->Lock();
+}
+
+bool FlagImpl::RestoreState(const CommandLineFlag& flag, const void* value,
+ bool modified, bool on_command_line,
+ int64_t counter) {
+ {
+ absl::MutexLock l(DataGuard());
+
+ if (counter_ == counter) return false;
+ }
+
+ Write(flag, value, op_);
+
+ {
+ absl::MutexLock l(DataGuard());
+
+ modified_ = modified;
+ on_command_line_ = on_command_line;
+ }
+
+ return true;
+}
+
+// Attempts to parse supplied `value` string using parsing routine in the `flag`
+// argument. If parsing successful, this function stores the parsed value in
+// 'dst' assuming it is a pointer to the flag's value type. In case if any error
+// is encountered in either step, the error message is stored in 'err'
+bool FlagImpl::TryParse(const CommandLineFlag& flag, void* dst,
+ absl::string_view value, std::string* err) const
+ ABSL_EXCLUSIVE_LOCKS_REQUIRED(locks_->primary_mu) {
+ void* tentative_value = Clone(op_, def_);
+ std::string parse_err;
+ if (!Parse(marshalling_op_, value, tentative_value, &parse_err)) {
+ auto type_name = flag.Typename();
+ absl::string_view err_sep = parse_err.empty() ? "" : "; ";
+ absl::string_view typename_sep = type_name.empty() ? "" : " ";
+ *err = absl::StrCat("Illegal value '", value, "' specified for",
+ typename_sep, type_name, " flag '", flag.Name(), "'",
+ err_sep, parse_err);
+ Delete(op_, tentative_value);
+ return false;
+ }
+
+ Copy(op_, tentative_value, dst);
+ Delete(op_, tentative_value);
+ return true;
+}
+
+void FlagImpl::Read(const CommandLineFlag& flag, void* dst,
+ const flags_internal::FlagOpFn dst_op) const {
+ absl::ReaderMutexLock l(DataGuard());
+
+ // `dst_op` is the unmarshaling operation corresponding to the declaration
+ // visibile at the call site. `op` is the Flag's defined unmarshalling
+ // operation. They must match for this operation to be well-defined.
+ if (ABSL_PREDICT_FALSE(dst_op != op_)) {
+ ABSL_INTERNAL_LOG(
+ ERROR,
+ absl::StrCat("Flag '", flag.Name(),
+ "' is defined as one type and declared as another"));
+ }
+ CopyConstruct(op_, cur_, dst);
+}
+
+void FlagImpl::StoreAtomic() ABSL_EXCLUSIVE_LOCKS_REQUIRED(locks_->primary_mu) {
+ size_t data_size = Sizeof(op_);
+
+ if (data_size <= sizeof(int64_t)) {
+ int64_t t = 0;
+ std::memcpy(&t, cur_, data_size);
+ atomic_.store(t, std::memory_order_release);
+ }
+}
+
+void FlagImpl::Write(const CommandLineFlag& flag, const void* src,
+ const flags_internal::FlagOpFn src_op) {
+ absl::MutexLock l(DataGuard());
+
+ // `src_op` is the marshalling operation corresponding to the declaration
+ // visible at the call site. `op` is the Flag's defined marshalling operation.
+ // They must match for this operation to be well-defined.
+ if (ABSL_PREDICT_FALSE(src_op != op_)) {
+ ABSL_INTERNAL_LOG(
+ ERROR,
+ absl::StrCat("Flag '", flag.Name(),
+ "' is defined as one type and declared as another"));
+ }
+
+ if (ShouldValidateFlagValue(flag)) {
+ void* obj = Clone(op_, src);
+ std::string ignored_error;
+ std::string src_as_str = Unparse(marshalling_op_, src);
+ if (!Parse(marshalling_op_, src_as_str, obj, &ignored_error)) {
+ ABSL_INTERNAL_LOG(ERROR,
+ absl::StrCat("Attempt to set flag '", flag.Name(),
+ "' to invalid value ", src_as_str));
+ }
+ Delete(op_, obj);
+ }
+
+ modified_ = true;
+ counter_++;
+ Copy(op_, src, cur_);
+
+ StoreAtomic();
+ InvokeCallback();
+}
+
+// Sets the value of the flag based on specified string `value`. If the flag
+// was successfully set to new value, it returns true. Otherwise, sets `err`
+// to indicate the error, leaves the flag unchanged, and returns false. There
+// are three ways to set the flag's value:
+// * Update the current flag value
+// * Update the flag's default value
+// * Update the current flag value if it was never set before
+// The mode is selected based on 'set_mode' parameter.
+bool FlagImpl::SetFromString(const CommandLineFlag& flag,
+ absl::string_view value, FlagSettingMode set_mode,
+ ValueSource source, std::string* err) {
+ absl::MutexLock l(DataGuard());
+
+ switch (set_mode) {
+ case SET_FLAGS_VALUE: {
+ // set or modify the flag's value
+ if (!TryParse(flag, cur_, value, err)) return false;
+ modified_ = true;
+ counter_++;
+ StoreAtomic();
+ InvokeCallback();
+
+ if (source == kCommandLine) {
+ on_command_line_ = true;
+ }
+ break;
+ }
+ case SET_FLAG_IF_DEFAULT: {
+ // set the flag's value, but only if it hasn't been set by someone else
+ if (!modified_) {
+ if (!TryParse(flag, cur_, value, err)) return false;
+ modified_ = true;
+ counter_++;
+ StoreAtomic();
+ InvokeCallback();
+ } else {
+ // TODO(rogeeff): review and fix this semantic. Currently we do not fail
+ // in this case if flag is modified. This is misleading since the flag's
+ // value is not updated even though we return true.
+ // *err = absl::StrCat(Name(), " is already set to ",
+ // CurrentValue(), "\n");
+ // return false;
+ return true;
+ }
+ break;
+ }
+ case SET_FLAGS_DEFAULT: {
+ // modify the flag's default-value
+ if (!TryParse(flag, def_, value, err)) return false;
+
+ if (!modified_) {
+ // Need to set both default value *and* current, in this case
+ Copy(op_, def_, cur_);
+ StoreAtomic();
+ InvokeCallback();
+ }
+ break;
+ }
+ }
+
+ return true;
+}
+
+void FlagImpl::CheckDefaultValueParsingRoundtrip(
+ const CommandLineFlag& flag) const {
+ std::string v = DefaultValue();
+
+ absl::MutexLock lock(DataGuard());
+
+ void* dst = Clone(op_, def_);
+ std::string error;
+ if (!flags_internal::Parse(marshalling_op_, v, dst, &error)) {
+ ABSL_INTERNAL_LOG(
+ FATAL,
+ absl::StrCat("Flag ", flag.Name(), " (from ", flag.Filename(),
+ "): std::string form of default value '", v,
+ "' could not be parsed; error=", error));
+ }
+
+ // We do not compare dst to def since parsing/unparsing may make
+ // small changes, e.g., precision loss for floating point types.
+ Delete(op_, dst);
+}
+
+bool FlagImpl::ValidateInputValue(absl::string_view value) const {
+ absl::MutexLock l(DataGuard());
+
+ void* obj = Clone(op_, def_);
+ std::string ignored_error;
+ const bool result =
+ flags_internal::Parse(marshalling_op_, value, obj, &ignored_error);
+ Delete(op_, obj);
+ return result;
}
} // namespace flags_internal