build: ensure we aren't using GNU extensions

Summary:
Remove the use of gnu extensions:
 - anonymous structs
 - variadic macros with no argument
And add a Clang warning for detecting their future use.

Backport of core [[bitcoin/bitcoin#18088 | PR18088]].

Test Plan:
With clang:
  ninja all check
Check there is no warning.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D9109

src/CMakeLists.txt

@@ -218,6 +218,7 @@ add_compiler_flags(
 	-Wall
 	-Wextra
 	-Wformat
+	-Wgnu
 	-Wvla
 	-Wcast-align
 	-Wunused-parameter

src/logging/timer.h

@@ -79,14 +79,11 @@ template <typename TimeType> class Timer {
 
 } // namespace BCLog
 
-#define LOG_TIME_MICROS(end_msg, ...)                                          \
-    BCLog::Timer<std::chrono::microseconds> PASTE2(                            \
-        logging_timer, __COUNTER__)(__func__, end_msg, ##__VA_ARGS__)
-#define LOG_TIME_MILLIS(end_msg, ...)                                          \
+#define LOG_TIME_MILLIS_WITH_CATEGORY(end_msg, log_category)                   \
     BCLog::Timer<std::chrono::milliseconds> PASTE2(                            \
-        logging_timer, __COUNTER__)(__func__, end_msg, ##__VA_ARGS__)
-#define LOG_TIME_SECONDS(end_msg, ...)                                         \
-    BCLog::Timer<std::chrono::seconds> PASTE2(logging_timer, __COUNTER__)(     \
-        __func__, end_msg, ##__VA_ARGS__)
+        logging_timer, __COUNTER__)(__func__, end_msg, log_category)
+#define LOG_TIME_SECONDS(end_msg)                                              \
+    BCLog::Timer<std::chrono::seconds> PASTE2(logging_timer,                   \
+                                              __COUNTER__)(__func__, end_msg)
 
 #endif // BITCOIN_LOGGING_TIMER_H

src/prevector.h

@@ -237,7 +237,7 @@ class prevector {
         struct {
             char *indirect;
             size_type capacity;
-        };
+        } indirect_contents;
     };
 #pragma pack(pop)
     alignas(char *) direct_or_indirect _union = {};
@@ -258,10 +258,11 @@ class prevector {
         return reinterpret_cast<const T *>(_union.direct) + pos;
     }
     T *indirect_ptr(difference_type pos) {
-        return reinterpret_cast<T *>(_union.indirect) + pos;
+        return reinterpret_cast<T *>(_union.indirect_contents.indirect) + pos;
     }
     const T *indirect_ptr(difference_type pos) const {
-        return reinterpret_cast<const T *>(_union.indirect) + pos;
+        return reinterpret_cast<const T *>(_union.indirect_contents.indirect) +
+               pos;
     }
     bool is_direct() const { return _size <= N; }
 
@@ -282,19 +283,20 @@ class prevector {
                 // allocator or new/delete so that handlers are called as
                 // necessary, but performance would be slightly degraded by
                 // doing so.
-                _union.indirect = static_cast<char *>(realloc(
-                    _union.indirect, ((size_t)sizeof(T)) * new_capacity));
-                assert(_union.indirect);
-                _union.capacity = new_capacity;
+                _union.indirect_contents.indirect = static_cast<char *>(
+                    realloc(_union.indirect_contents.indirect,
+                            ((size_t)sizeof(T)) * new_capacity));
+                assert(_union.indirect_contents.indirect);
+                _union.indirect_contents.capacity = new_capacity;
             } else {
                 char *new_indirect = static_cast<char *>(
                     malloc(((size_t)sizeof(T)) * new_capacity));
                 assert(new_indirect);
                 T *src = direct_ptr(0);
                 T *dst = reinterpret_cast<T *>(new_indirect);
                 memcpy(dst, src, size() * sizeof(T));
-                _union.indirect = new_indirect;
-                _union.capacity = new_capacity;
+                _union.indirect_contents.indirect = new_indirect;
+                _union.indirect_contents.capacity = new_capacity;
                 _size += N + 1;
             }
         }
@@ -403,7 +405,7 @@ class prevector {
         if (is_direct()) {
             return N;
         } else {
-            return _union.capacity;
+            return _union.indirect_contents.capacity;
         }
     }
 
@@ -548,8 +550,8 @@ class prevector {
             clear();
         }
         if (!is_direct()) {
-            free(_union.indirect);
-            _union.indirect = nullptr;
+            free(_union.indirect_contents.indirect);
+            _union.indirect_contents.indirect = nullptr;
         }
     }
 
@@ -601,7 +603,7 @@ class prevector {
         if (is_direct()) {
             return 0;
         } else {
-            return ((size_t)(sizeof(T))) * _union.capacity;
+            return ((size_t)(sizeof(T))) * _union.indirect_contents.capacity;
         }
     }
 

src/validation.cpp

@@ -2111,12 +2111,13 @@ bool CChainState::FlushStateToDisk(const CChainParams &chainparams,
             if (fPruneMode && (fCheckForPruning || nManualPruneHeight > 0) &&
                 !fReindex) {
                 if (nManualPruneHeight > 0) {
-                    LOG_TIME_MILLIS("find files to prune (manual)",
-                                    BCLog::BENCH);
+                    LOG_TIME_MILLIS_WITH_CATEGORY(
+                        "find files to prune (manual)", BCLog::BENCH);
                     FindFilesToPruneManual(g_chainman, setFilesToPrune,
                                            nManualPruneHeight);
                 } else {
-                    LOG_TIME_MILLIS("find files to prune", BCLog::BENCH);
+                    LOG_TIME_MILLIS_WITH_CATEGORY("find files to prune",
+                                                  BCLog::BENCH);
                     FindFilesToPrune(g_chainman, setFilesToPrune,
                                      chainparams.PruneAfterHeight());
                     fCheckForPruning = false;
@@ -2166,8 +2167,8 @@ bool CChainState::FlushStateToDisk(const CChainParams &chainparams,
                 }
 
                 {
-                    LOG_TIME_MILLIS("write block and undo data to disk",
-                                    BCLog::BENCH);
+                    LOG_TIME_MILLIS_WITH_CATEGORY(
+                        "write block and undo data to disk", BCLog::BENCH);
 
                     // First make sure all block and undo data is flushed to
                     // disk.
@@ -2176,7 +2177,8 @@ bool CChainState::FlushStateToDisk(const CChainParams &chainparams,
                 // Then update all block file information (which may refer to
                 // block and undo files).
                 {
-                    LOG_TIME_MILLIS("write block index to disk", BCLog::BENCH);
+                    LOG_TIME_MILLIS_WITH_CATEGORY("write block index to disk",
+                                                  BCLog::BENCH);
 
                     std::vector<std::pair<int, const CBlockFileInfo *>> vFiles;
                     vFiles.reserve(setDirtyFileInfo.size());
@@ -2203,7 +2205,8 @@ bool CChainState::FlushStateToDisk(const CChainParams &chainparams,
 
                 // Finally remove any pruned files
                 if (fFlushForPrune) {
-                    LOG_TIME_MILLIS("unlink pruned files", BCLog::BENCH);
+                    LOG_TIME_MILLIS_WITH_CATEGORY("unlink pruned files",
+                                                  BCLog::BENCH);
 
                     UnlinkPrunedFiles(setFilesToPrune);
                 }