help: improve feature descriptions

oi/Features.cpp

@@ -16,8 +16,39 @@
 #include "Features.h"
 
 #include <map>
+#include <numeric>
+#include <stdexcept>
 
 namespace ObjectIntrospection {
+namespace {
+
+std::string_view featureHelp(Feature f) {
+  switch (f) {
+    case Feature::ChaseRawPointers:
+      return "Chase raw pointers in the probed object.";
+    case Feature::PackStructs:
+      return "Pack structs.";
+    case Feature::GenPaddingStats:
+      return "Generate statistics on padding of structures.";
+    case Feature::CaptureThriftIsset:
+      return "Capture isset data for Thrift object.";
+    case Feature::TypeGraph:
+      return "Use Type Graph for code generation (CodeGen V2).";
+    case Feature::TypedDataSegment:
+      return "Use Typed Data Segment in generated code.";
+    case Feature::GenJitDebug:
+      return "Generate debug information for the JIT object.";
+    case Feature::JitLogging:
+      return "Log information from the JIT code for debugging.";
+    case Feature::PolymorphicInheritance:
+      return "Follow polymorphic inheritance hierarchies in the probed object.";
+
+    case Feature::UnknownFeature:
+      throw std::runtime_error("should not ask for help for UnknownFeature!");
+  }
+}
+
+}  // namespace
 
 Feature featureFromStr(std::string_view str) {
   static const std::map<std::string_view, Feature> nameMap = {
@@ -45,4 +76,20 @@ const char* featureToStr(Feature f) {
   }
 }
 
+void featuresHelp(std::ostream& out) {
+  out << "FEATURES SUMMARY" << std::endl;
+
+  size_t longestName = std::accumulate(
+      allFeatures.begin(), allFeatures.end(), 0, [](size_t acc, Feature f) {
+        return std::max(acc, std::string_view(featureToStr(f)).size());
+      });
+
+  for (Feature f : allFeatures) {
+    std::string_view name(featureToStr(f));
+
+    out << "  " << name << std::string(longestName - name.size() + 2, ' ')
+        << featureHelp(f) << std::endl;
+  }
+}
+
 }  // namespace ObjectIntrospection

oi/Features.h

@@ -16,6 +16,7 @@
 #pragma once
 
 #include <array>
+#include <ostream>
 #include <string_view>
 
 #include "oi/EnumBitset.h"
@@ -42,6 +43,7 @@ enum class Feature {
 
 Feature featureFromStr(std::string_view);
 const char* featureToStr(Feature);
+void featuresHelp(std::ostream& out);
 
 constexpr std::array allFeatures = {
 #define X(name, _) Feature::name,

oi/OID.cpp

@@ -146,24 +146,17 @@ constexpr static OIOpts opts{
     OIOpt{'m', "mode", required_argument, "[prod]",
           "Allows to specify a mode of operation/group of settings"},
     OIOpt{'f', "enable-feature", required_argument, nullptr,
-          "Enable a specific feature: ["
-#define X(name, str) str ","
-          OI_FEATURE_LIST
-#undef X
-          "]"},
+          "Enable feature FEATURE"},
     OIOpt{'F', "disable-feature", required_argument, nullptr,
-          "Disable a specific feature: ["
-#define X(name, str) str ","
-          OI_FEATURE_LIST
-#undef X
-          "]"},
+          "Disable feature FEATURE"},
 };
 
 void usage() {
-  std::cout << "usage: oid ...\n";
-  std::cout << opts;
+  std::cerr << "usage: oid ...\n";
+  std::cerr << opts << std::endl;
+  featuresHelp(std::cerr);
 
-  std::cout << "\n\tFor problem reporting, questions and general comments "
+  std::cerr << "\n\tFor problem reporting, questions and general comments "
                "please pop along"
                "\n\tto the Object Introspection Workplace group at "
                "https://fburl.com/oid.\n"

tools/OITB.cpp

@@ -43,17 +43,9 @@ constexpr static OIOpts opts{
           "File to dump the results to, as JSON\n"
           "(in addition to the default RocksDB output)"},
     OIOpt{'f', "enable-feature", required_argument, nullptr,
-          "Enable a specific feature: ["
-#define X(name, str) str ","
-          OI_FEATURE_LIST
-#undef X
-          "]"},
+          "Enable feature FEATURE"},
     OIOpt{'F', "disable-feature", required_argument, nullptr,
-          "Disable a specific feature: ["
-#define X(name, str) str ","
-          OI_FEATURE_LIST
-#undef X
-          "]"},
+          "Disable feature FEATURE"},
 };
 
 static void usage(std::ostream& out) {
@@ -65,7 +57,8 @@ static void usage(std::ostream& out) {
 
   out << "\nusage: oitb [opts...] [--] <path-th> <path-pd> "
          "<path-dataseg-dump>\n";
-  out << opts;
+  out << opts << std::endl;
+  featuresHelp(out);
 
   out << std::endl;
 }