std.debug: dumpStackTrace & friends use DirectAllocator

this has the downside of failing to print a stack trace
when the system is out of memory (maybe we could add a
FallbackAllocator which tries DirectAllocator and falls
back on the 200KB preallocated buffer).

but for the more common use case when the system is not
out of memory, but the debug info cannot fit in
std.debug.global_allocator, now stack traces will work.

this is the case for the self hosted compiler.

1 files changed, 20 insertions, 5 deletions

diff --git a/std/debug/index.zig b/std/debug/index.zig
index a573dc5549..9057f157de 100644
--- a/std/debug/index.zig
+++ b/std/debug/index.zig
@@ -38,7 +38,7 @@ pub fn getSelfDebugInfo() !&ElfStackTrace {
     if (self_debug_info) |info| {
         return info;
     } else {
-        const info = try openSelfDebugInfo(global_allocator);
+        const info = try openSelfDebugInfo(getDebugInfoAllocator());
         self_debug_info = info;
         return info;
     }
@@ -51,7 +51,7 @@ pub fn dumpCurrentStackTrace(start_addr: ?usize) void {
         stderr.print("Unable to dump stack trace: Unable to open debug info: {}\n", @errorName(err)) catch return;
         return;
     };
-    writeCurrentStackTrace(stderr, global_allocator, debug_info, stderr_file.isTty(), start_addr) catch |err| {
+    writeCurrentStackTrace(stderr, getDebugInfoAllocator(), debug_info, stderr_file.isTty(), start_addr) catch |err| {
         stderr.print("Unable to dump stack trace: {}\n", @errorName(err)) catch return;
         return;
     };
@@ -64,7 +64,7 @@ pub fn dumpStackTrace(stack_trace: &const builtin.StackTrace) void {
         stderr.print("Unable to dump stack trace: Unable to open debug info: {}\n", @errorName(err)) catch return;
         return;
     };
-    writeStackTrace(stack_trace, stderr, global_allocator, debug_info, stderr_file.isTty()) catch |err| {
+    writeStackTrace(stack_trace, stderr, getDebugInfoAllocator(), debug_info, stderr_file.isTty()) catch |err| {
         stderr.print("Unable to dump stack trace: {}\n", @errorName(err)) catch return;
         return;
     };
@@ -592,8 +592,8 @@ fn getString(st: &ElfStackTrace, offset: u64) ![]u8 {
 }
 
 fn readAllocBytes(allocator: &mem.Allocator, in_stream: var, size: usize) ![]u8 {
-    const buf = try global_allocator.alloc(u8, size);
-    errdefer global_allocator.free(buf);
+    const buf = try allocator.alloc(u8, size);
+    errdefer allocator.free(buf);
     if ((try in_stream.read(buf)) < size) return error.EndOfFile;
     return buf;
 }
@@ -1126,6 +1126,21 @@ fn readILeb128(in_stream: var) !i64 {
     }
 }
 
+/// This should only be used in temporary test programs.
 pub const global_allocator = &global_fixed_allocator.allocator;
 var global_fixed_allocator = std.heap.FixedBufferAllocator.init(global_allocator_mem[0..]);
 var global_allocator_mem: [100 * 1024]u8 = undefined;
+
+
+// TODO make thread safe
+var debug_info_allocator: ?&mem.Allocator = null;
+var debug_info_direct_allocator: std.heap.DirectAllocator = undefined;
+var debug_info_arena_allocator: std.heap.ArenaAllocator = undefined;
+fn getDebugInfoAllocator() &mem.Allocator {
+    if (debug_info_allocator) |a| return a;
+
+    debug_info_direct_allocator = std.heap.DirectAllocator.init();
+    debug_info_arena_allocator = std.heap.ArenaAllocator.init(&debug_info_direct_allocator.allocator);
+    debug_info_allocator = &debug_info_arena_allocator.allocator;
+    return &debug_info_arena_allocator.allocator;
+}