medfall

commit b74e61a913527babd16001995bc56da3a79393a2
parent 52ea14acaae25db2bbacfe22084f665a3b003677
Author: Michael Savage <mikejsavage@gmail.com>
Date:   Wed Oct 12 18:54:56 +0300

Drop into GDB when the game crashes on Linux

Diffstat:
autogdb.h
 | 
72
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
main.cc
 | 
9
+++++++++
2 files changed, 81 insertions(+), 0 deletions(-)
diff --git a/autogdb.h b/autogdb.h
@@ -0,0 +1,72 @@
+#ifndef _AUTOGDB_H_
+#define _AUTOGDB_H_
+
+#include <sys/ptrace.h>
+#include <sys/wait.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include <err.h>
+
+static void prompt_to_run_gdb( int signal ) {
+	const char * signal_names[ NSIG ];
+	signal_names[ SIGABRT ] = "SIGABRT";
+	signal_names[ SIGILL ] = "SIGILL";
+	signal_names[ SIGSEGV ] = "SIGSEGV";
+
+	char crashed_pid[ 16 ];
+	snprintf( crashed_pid, sizeof( crashed_pid ), "%d", getpid() );
+	printf( "PID %s received %s. Debug? (y/n)\n", crashed_pid, signal_names[ signal ] );
+
+	char c;
+	read( STDIN_FILENO, &c, 1 );
+	if( c != 'y' ) exit( 1 );
+
+	// fork off and run gdb
+	pid_t child_pid = fork();
+	if( child_pid == -1 ) err( 1, "fork" );
+
+	if( child_pid == 0 ) {
+		execlp( "gdbx", "gdbx", "--", "-p", crashed_pid, ( char * ) 0 );
+		execlp( "gdb", "gdb", "-p", crashed_pid, ( char * ) 0 );
+		err( 1, "execlp" );
+	}
+
+	// pause the parent while we wait for gdb to attach
+	pause();
+}
+
+static void install_debug_signal_handlers() {
+	signal( SIGABRT, prompt_to_run_gdb );
+	signal( SIGILL, prompt_to_run_gdb );
+	signal( SIGSEGV, prompt_to_run_gdb );
+}
+
+static bool being_debugged() {
+	pid_t parent_pid = getpid();
+	pid_t child_pid = fork();
+	if( child_pid == -1 ) err( 1, "fork" );
+
+	if( child_pid == 0 ) {
+		// if we can't ptrace the parent then gdb is already there
+		if( ptrace( PTRACE_ATTACH, parent_pid, NULL, NULL ) != 0 ) exit( 1 );
+
+		// ptrace automatically stops the process so wait for SIGSTOP and send PTRACE_CONT
+		waitpid( parent_pid, NULL, 0 );
+		ptrace( PTRACE_CONT, NULL, NULL );
+
+		// detach
+		ptrace( PTRACE_DETACH, parent_pid, NULL, NULL );
+		exit( 0 );
+	}
+
+	int status;
+	waitpid( child_pid, &status, 0 );
+	if( !WIFEXITED( status ) ) err( 1, "WIFEXITED" );
+
+	return WEXITSTATUS( status ) == 1;
+}
+
+#endif // _AUTOGDB_H_
diff --git a/main.cc b/main.cc
@@ -14,6 +14,7 @@
 #include "intrinsics.h"
 #include "gl.h"
 #include "keys.h"
+#include "platform.h"
 #include "platform_library.h"
 
 struct Game {
@@ -72,7 +73,15 @@ static bool should_reload_game( const char * const path, const time_t lib_write_
 	return file_last_write_time( path ) > lib_write_time;
 }
 
+#if PLATFORM_LINUX
+#include "autogdb.h"
+#endif
+
 int main( int argc, char ** argv ) {
+#if PLATFORM_LINUX
+	install_debug_signal_handlers();
+#endif
+
 	const char * game_library_path = argc == 2 ? argv[ 1 ] : "./hm.so";
 
 	size_t persistent_size = megabytes( 64 );