From 76e12c994db35dc582255dff7dadf4029ac7e657 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Mon, 25 Apr 2022 18:48:28 +0100
Subject: [PATCH] Crash log: Write log to file and console as it is being
 generated on Unix

---
 src/crashlog.cpp | 43 +++++++++++++++++++++++++++++++++++++------
 src/crashlog.h   |  5 ++++-
 2 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/src/crashlog.cpp b/src/crashlog.cpp
index 96c3a35ea6..07a16f7c2c 100644
--- a/src/crashlog.cpp
+++ b/src/crashlog.cpp
@@ -432,7 +432,7 @@ char *CrashLog::LogCommandLog(char *buffer, const char *last) const
  * @param last   The last position in the buffer to write to.
  * @return the position of the \c '\0' character after the buffer.
  */
-char *CrashLog::FillCrashLog(char *buffer, const char *last) const
+char *CrashLog::FillCrashLog(char *buffer, const char *last)
 {
 	buffer += seprintf(buffer, last, "*** OpenTTD Crash Report ***\n\n");
 
@@ -452,10 +452,13 @@ char *CrashLog::FillCrashLog(char *buffer, const char *last) const
 	}
 	buffer += seprintf(buffer, last, "\n");
 
+	this->FlushCrashLogBuffer();
+
 	buffer = this->LogError(buffer, last, CrashLog::message);
 
 #ifdef USE_SCOPE_INFO
 	if (IsMainThread() || IsGameThread()) {
+		this->FlushCrashLogBuffer();
 		buffer += WriteScopeLog(buffer, last);
 	}
 #endif
@@ -467,9 +470,13 @@ char *CrashLog::FillCrashLog(char *buffer, const char *last) const
 	}
 
 	buffer = this->LogOpenTTDVersion(buffer, last);
+	this->FlushCrashLogBuffer();
 	buffer = this->LogStacktrace(buffer, last);
+	this->FlushCrashLogBuffer();
 	buffer = this->LogRegisters(buffer, last);
+	this->FlushCrashLogBuffer();
 	buffer = this->LogOSVersion(buffer, last);
+	this->FlushCrashLogBuffer();
 	buffer = this->LogCompiler(buffer, last);
 	buffer = this->LogOSVersionDetail(buffer, last);
 	buffer = this->LogConfiguration(buffer, last);
@@ -643,7 +650,7 @@ bool CrashLog::WriteCrashLog(const char *buffer, char *filename, const char *fil
 	if (file == nullptr) return false;
 
 	size_t len = strlen(buffer);
-	size_t written = fwrite(buffer, 1, len, file);
+	size_t written = (len != 0) ? fwrite(buffer, 1, len, file) : 0;
 
 	if (crashlog_file) {
 		*crashlog_file = file;
@@ -653,6 +660,23 @@ bool CrashLog::WriteCrashLog(const char *buffer, char *filename, const char *fil
 	return len == written;
 }
 
+void CrashLog::FlushCrashLogBuffer()
+{
+	if (this->crash_buffer_write == nullptr) return;
+
+	size_t len = strlen(this->crash_buffer_write);
+	if (len == 0) return;
+
+	if (this->crash_file != nullptr) {
+		fwrite(this->crash_buffer_write, 1, len, this->crash_file);
+		fflush(this->crash_file);
+	}
+	fwrite(this->crash_buffer_write, 1, len, stdout);
+	fflush(stdout);
+
+	this->crash_buffer_write += len;
+}
+
 /* virtual */ int CrashLog::WriteCrashDump(char *filename, const char *filename_last) const
 {
 	/* Stub implementation; not all OSes support this. */
@@ -771,18 +795,25 @@ bool CrashLog::MakeCrashLog(char *buffer, const char *last)
 	bool ret = true;
 
 	printf("Crash encountered, generating crash log...\n");
-	this->FillCrashLog(buffer, last);
-	printf("%s\n", buffer);
-	printf("Crash log generated.\n\n");
 
 	printf("Writing crash log to disk...\n");
-	bool bret = this->WriteCrashLog(buffer, filename, lastof(filename), this->name_buffer);
+	bool bret = this->WriteCrashLog("", filename, lastof(filename), this->name_buffer, &(this->crash_file));
 	if (bret) {
 		printf("Crash log written to %s. Please add this file to any bug reports.\n\n", filename);
 	} else {
 		printf("Writing crash log failed. Please attach the output above to any bug reports.\n\n");
 		ret = false;
 	}
+	this->crash_buffer_write = buffer;
+
+	this->FillCrashLog(buffer, last);
+	this->FlushCrashLogBuffer();
+	if (this->crash_file != nullptr) {
+		FioFCloseFile(this->crash_file);
+		this->crash_file = nullptr;
+	}
+	printf("Crash log generated.\n\n");
+
 
 	/* Don't mention writing crash dumps because not all platforms support it. */
 	int dret = this->WriteCrashDump(filename, lastof(filename));
diff --git a/src/crashlog.h b/src/crashlog.h
index 176fe832f9..f9c38fca46 100644
--- a/src/crashlog.h
+++ b/src/crashlog.h
@@ -131,11 +131,14 @@ protected:
 public:
 	/** Buffer for the filename name prefix */
 	char name_buffer[64];
+	FILE *crash_file = nullptr;
+	const char *crash_buffer_write = nullptr;
 
 	/** Stub destructor to silence some compilers. */
 	virtual ~CrashLog() {}
 
-	char *FillCrashLog(char *buffer, const char *last) const;
+	char *FillCrashLog(char *buffer, const char *last);
+	void FlushCrashLogBuffer();
 	char *FillDesyncCrashLog(char *buffer, const char *last, const DesyncExtraInfo &info) const;
 	char *FillInconsistencyLog(char *buffer, const char *last, const InconsistencyExtraInfo &info) const;
 	char *FillVersionInfoLog(char *buffer, const char *last) const;