Refactor and improve crash handler stderr dumps

1. Prevent concurrent crashes to interleave in stderr
2. Cleaner and more compact formatting of registers dump
3. Omit `OLDMASK` (nobody seems to know what is it for)
4. Don't print the top backtrace frame twice
5. Code cosmetics
commit_hash:f7a4c960b3400d6dfb0f8f60317aa524611d2fd0

3 files changed, 10 insertions, 25 deletions

diff --git a/library/cpp/yt/backtrace/symbolizers/dummy/dummy_symbolizer.cpp b/library/cpp/yt/backtrace/symbolizers/dummy/dummy_symbolizer.cpp
index 19cb41e7951..3b1d37aa028 100644
--- a/library/cpp/yt/backtrace/symbolizers/dummy/dummy_symbolizer.cpp
+++ b/library/cpp/yt/backtrace/symbolizers/dummy/dummy_symbolizer.cpp
@@ -13,8 +13,8 @@ void SymbolizeBacktrace(
     for (int index = 0; index < std::ssize(backtrace); ++index) {
         TRawFormatter<1024> formatter;
         formatter.AppendNumber(index + 1, 10, 2);
-        formatter.AppendString(". ");
-        formatter.AppendNumberAsHexWithPadding(reinterpret_cast<uintptr_t>(backtrace[index]), 12);
+        formatter.AppendString(". 0x");
+        formatter.AppendNumber(reinterpret_cast<uintptr_t>(backtrace[index]), /*radix*/ 16, /*width*/ 12);
         formatter.AppendString("\n");
         frameCallback(formatter.GetBuffer());
     }
diff --git a/library/cpp/yt/backtrace/symbolizers/dynload/dynload_symbolizer.cpp b/library/cpp/yt/backtrace/symbolizers/dynload/dynload_symbolizer.cpp
index 37ebda8e488..ca4b157045b 100644
--- a/library/cpp/yt/backtrace/symbolizers/dynload/dynload_symbolizer.cpp
+++ b/library/cpp/yt/backtrace/symbolizers/dynload/dynload_symbolizer.cpp
@@ -75,10 +75,10 @@ int GetSymbolInfo(const void* pc, char* buffer, int length)
 
 void DumpStackFrameInfo(TBaseFormatter* formatter, const void* pc)
 {
-    formatter->AppendString("@ ");
+    formatter->AppendString("@ 0x");
     const int width = (sizeof(void*) == 8 ? 12 : 8) + 2;
     // +2 for "0x"; 12 for x86_64 because higher bits are always zeroed.
-    formatter->AppendNumberAsHexWithPadding(reinterpret_cast<uintptr_t>(pc), width);
+    formatter->AppendNumber(reinterpret_cast<uintptr_t>(pc), 16, width);
     formatter->AppendString(" ");
     // Get the symbol from the previous address of PC,
     // because PC may be in the next function.
diff --git a/library/cpp/yt/string/raw_formatter.h b/library/cpp/yt/string/raw_formatter.h
index 6956330883b..23ea7f9af08 100644
--- a/library/cpp/yt/string/raw_formatter.h
+++ b/library/cpp/yt/string/raw_formatter.h
@@ -84,11 +84,12 @@ public:
         }
     }
 
-    //! Appends a single character and updates the internal cursor.
-    void AppendChar(char ch)
+    //! Appends a single character given number of times and updates the internal cursor.
+    void AppendChar(char ch, int count = 1)
     {
-        if (Cursor_ < End_) {
+        while (Cursor_ < End_ && count > 0) {
             *Cursor_++ = ch;
+            count--;
         }
     }
 
@@ -97,6 +98,8 @@ public:
     {
         int digits = 0;
 
+        width = std::min(width, GetBytesRemaining());
+
         if (radix == 16) {
             // Optimize output of hex numbers.
 
@@ -140,22 +143,6 @@ public:
         }
     }
 
-    //! Formats |number| as hexadecimal number and updates the internal cursor.
-    //! Padding will be added in front if needed.
-    void AppendNumberAsHexWithPadding(uintptr_t number, int width)
-    {
-        char* begin = Cursor_;
-        AppendString("0x");
-        AppendNumber(number, 16);
-        // Move to right and add padding in front if needed.
-        if (Cursor_ < begin + width) {
-            auto delta = begin + width - Cursor_;
-            std::copy(begin, Cursor_, begin + delta);
-            std::fill(begin, begin + delta, ' ');
-            Cursor_ = begin + width;
-        }
-    }
-
     //! Formats |guid| and updates the internal cursor.
     void AppendGuid(TGuid guid)
     {
@@ -185,7 +172,6 @@ private:
     char* const Begin_;
     char* Cursor_;
     char* const End_;
-
 };
 
 template <size_t N>
@@ -203,7 +189,6 @@ public:
 
 private:
     char Buffer_[N];
-
 };
 
 ////////////////////////////////////////////////////////////////////////////////