-fstrip removes exported symbols when building executable

[noctice007]

Summary

When using the -fstrip flag with zig build-exe, the exported symbols are removed from the resulting binary, which seems unexpected.

Steps to Reproduce

1. Create a file main.zig with the following content:

   export fn foo() void {}
   pub fn main() void {}

2. Run the following command:

   zig build-exe main.zig -fstrip
   

3. Attempt to disassemble the foo function in the resulting binary:

   objdump main --disassemble=foo
   

Observed Behavior

Output

main:     file format elf64-x86-64


Disassembly of section .text:
<blank>

The foo section is not found, indicating that the -fstrip flag removed the exported symbol.

Expected Behavior

The foo function, being explicitly marked as export, should remain accessible in the binary, even when -fstrip is used

Environment

• Zig version: 0.13.0
• OS: Arch linux x86_64

Additional Note

If this behavior is intentional, clarification in the documentation would be helpful. If not, this might be a bug with -fstrip implementation.

[alexrp]

You probably want -rdynamic.

[noctice007]

You probably want -rdynamic.

I'm not an expert in low level and assembly output generation
but adding -rdynamic increases the size of the executable to 161K from 8.2K in my machine
The base command is:

zig build-exe main.zig -OReleaseFast -fstrip -fsingle-threaded

This gives the smaller size version of the executable
Is this the wanted behavior?

[alexrp]

Well, what exactly is your goal? It normally doesn't make a ton of sense to export a function from an executable, which is why you have to opt into it with -rdynamic, and why -fstrip happily strips that symbol name by default (the symbol name is considered useless, strippable data if it's not exported by way of -rdynamic).

[noctice007]

Thanks for the explanation. I get that exporting functions from an executable isn’t a common thing and that using -rdynamic is the intentional way to opt into it. Still, the increase in size from -rdynamic feels a bit off, especially since small binary sizes is one of Zig selling point.

In cases where you really need to export just one or two functions, it feels like the current approach punishes that use case by adding unnecessary bloat. I get that -fstrip is doing what it’s supposed to, but the trade-off here feels a little inconvenient when the goal is keeping the binary lean while still exporting something essential.

I get it if this is just how it’s designed to work, but it feels like a tricky spot for people in this specific situation.

[alexrp]

To be clear, we only advertise small binary sizes for -O ReleaseSmall. I'm not completely sure what the size increase here is coming from; that needs investigating. It does look suspect.

The good news, though, is that if you use -lc (which you probably should if you're expecting to use dynamic linking), then the size increase from -O ReleaseSmall -fstrip -lc to -O ReleaseSmall -fstrip -lc -rdynamic is just 4.9K to 5.3K.

[noctice007]

what does -lc do
I haven't found the documentation for it in both zig build-exe --help and zig build-lib --help

[Rexicon226]

what does -lc do

It links libc.

[andrewrk]

Working as designed