zig

commit 33a779c7f65b9eb5115253bfe1cf4f4ea86336af (tree)
parent 673ae5b457479760ff8e08b3e06917a4b2651436
Author: Andrew Kelley <andrew@ziglang.org>
Date:   Fri, 28 May 2021 13:17:04 -0700

start.zig: intentional silent failure when cannot increase stack size

Diffstat:
M
lib/std/start.zig
 | 
24
++++++++++++------------

1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/lib/std/start.zig b/lib/std/start.zig
@@ -297,9 +297,10 @@ fn posixCallMainAndExit() noreturn {
             std.os.linux.tls.initStaticTLS();
         }
 
-        // Linux ignores the stack size from the ELF file, and instead always gives 8 MiB.
-        // Here we look for the stack size in our program headers and tell the kernel,
-        // no, seriously, give me that stack space, I wasn't joking.
+        // The way Linux executables represent stack size is via the PT_GNU_STACK
+        // program header. However the kernel does not recognize it; it always gives 8 MiB.
+        // Here we look for the stack size in our program headers and use setrlimit
+        // to ask for more stack space.
         {
             var i: usize = 0;
             var at_phdr: usize = undefined;
@@ -330,15 +331,14 @@ fn expandStackSize(at_phdr: usize, at_phnum: usize) void {
                     .cur = wanted_stack_size,
                     .max = wanted_stack_size,
                 }) catch {
-                    // If this is a debug build, it will be useful to find out
-                    // why this failed. If it is a release build, we allow the
-                    // stack overflow to cause a segmentation fault. Memory safety
-                    // is not compromised, however, depending on runtime state,
-                    // the application may crash due to provided stack space not
-                    // matching the known upper bound.
-                    if (builtin.mode == .Debug) {
-                        @panic("unable to increase stack size");
-                    }
+                    // Because we could not increase the stack size to the upper bound,
+                    // depending on what happens at runtime, a stack overflow may occur.
+                    // However it would cause a segmentation fault, thanks to stack probing,
+                    // so we do not have a memory safety issue here.
+                    // This is intentional silent failure.
+                    // This logic should be revisited when the following issues are addressed:
+                    // https://github.com/ziglang/zig/issues/157
+                    // https://github.com/ziglang/zig/issues/1006
                 };
                 break;
             },