std.zig.system.NativeTargetInfo: look for a shebang line in /usr/bin/env, if any

[BratishkaErik]

UPD: See #12151 (review)

[BratishkaErik]

For example, Gentoo's sys-apps/coreutils with USE flag multicall, or Red Hat Universal Base Image 9's coreutils-single #12156 (comment)

[andrewrk]

On which system do you observe /usr/bin/env not being an ELF file? And what is it instead?

[BratishkaErik]

On which system do you observe /usr/bin/env not being an ELF file? And what is it instead?

#12151 (comment)

It can be a script instead:

#!/usr/bin/coreutils --coreutils-prog-shebang=env

or similar.

[andrewrk]

Thanks for the info!

Here is my serious suggestion: modify the code to look for a shebang line in /usr/bin/env. If it finds one, then instead of using /usr/bin/env as the ELF file to examine, it uses the file it references instead. In the above example, it would therefore examine /usr/bin/coreutils (doing the same logic recursively in case it finds another script).

I think that this will be more robust than checking for hard-coded /usr/bin/bash.

[topolarity]

I think you're hitting a stage1 compiler bug. This diff seems to get things working again:

index c5b9454c9..d9467fe2a 100644
--- a/lib/std/zig/system/NativeTargetInfo.zig
+++ b/lib/std/zig/system/NativeTargetInfo.zig
@@ -390,19 +390,16 @@ fn detectAbiAndDynamicLinker(

                 else => |e| return e,
             };
-            var should_close = true;
-            defer if (should_close) file.close();

             const line = file.reader().readUntilDelimiter(&buffer, '\n') catch {
-                should_close = false;
                 break :blk file;
             };
             if (mem.startsWith(u8, line, "#!")) {
                 var it = std.mem.tokenize(u8, line[2..], " ");
                 file_name = it.next() orelse return defaultAbiAndDynamicLinker(cpu, os, cross_target);
+                file.close();
                 continue;
             } else {
-                should_close = false;
                 break :blk file;
             }
         }

[BratishkaErik]

I think you're hitting a stage1 compiler bug.
This diff seems to get things working again:

index c5b9454c9..d9467fe2a 100644
--- a/lib/std/zig/system/NativeTargetInfo.zig
+++ b/lib/std/zig/system/NativeTargetInfo.zig
@@ -390,19 +390,16 @@ fn detectAbiAndDynamicLinker(

                 else => |e| return e,
             };
-            var should_close = true;
-            defer if (should_close) file.close();

             const line = file.reader().readUntilDelimiter(&buffer, '\n') catch {
-                should_close = false;
                 break :blk file;
             };
             if (mem.startsWith(u8, line, "#!")) {
                 var it = std.mem.tokenize(u8, line[2..], " ");
                 file_name = it.next() orelse return defaultAbiAndDynamicLinker(cpu, os, cross_target);
+                file.close();
                 continue;
             } else {
-                should_close = false;
                 break :blk file;
             }
         }

Thank you!

[topolarity]

@marler8997 's suggestion is a good one, assuming it doesn't affect upstream error handling

Changes look good though 👍

[BratishkaErik]

Thank you for your helpful reviews! :)