Missing math symbols starting from nightly-2024-04-15

[Enet4]

Starting from nightly-2024-04-15, there was an update to compiler_builtins which changed the way that math functions are linked (https://github.com/rust-lang/compiler-builtins/pull/577). As a consequence, programs combining converted objects fail to build and link with the DJGPP toolchain because it cannot find the various functions in compiler_builtins::math.

I've been looking into this problem here and I'm thinking whether it would be best resolved at elf2djgpp directly. Would it make sense to also translate symbols in compiler_builtins::math using this tool?

---

As it turns out, I could reproduce the same problem with the example project after a few changes:

cd example
./build-dos-lib.sh
Converting ELF objects to COFF-GO32...
[WARN] Replacing bad extern compiler_builtins::mem::memcpy::h812ddf986f30a505 with memcpy
[WARN] Replacing bad extern compiler_builtins::mem::memset::hf5e04de1043dcb43 with memset
[WARN] Replacing bad extern compiler_builtins::mem::memcmp::hccf529a20986adb3 with memcmp
[WARN] Replacing bad extern compiler_builtins::mem::bcmp::h08ab184912ed088e with bcmp
[WARN] Replacing bad extern compiler_builtins::mem::memmove::h1be8968bbec95ef8 with memmove
build/debug/librust_lib.a built

make debug

i686-pc-msdosdjgpp-gcc -g -O0 -o build/debug/example.exe example.c build/debug/librust_lib.a
/usr/lib/gcc/i686-pc-msdosdjgpp/14.1.0/../../../../i686-pc-msdosdjgpp/bin/ld: build/debug/librust_lib.a(compiler_builtins-959ba4b0dcda654e.compiler_builtins.25b58a9b9e6e87fe-cgu.1.rcgu.o):compiler_builtins.25b58a9b9e6e87fe-cgu.1:(.text+0xc): undefined reference to `compiler_builtins::math::round'
/usr/lib/gcc/i686-pc-msdosdjgpp/14.1.0/../../../../i686-pc-msdosdjgpp/bin/ld: build/debug/librust_lib.a(compiler_builtins-959ba4b0dcda654e.compiler_builtins.25b58a9b9e6e87fe-cgu.1.rcgu.o):compiler_builtins.25b58a9b9e6e87fe-cgu.1:(.text+0xc): undefined reference to `compiler_builtins::math::trunc'
/usr/lib/gcc/i686-pc-msdosdjgpp/14.1.0/../../../../i686-pc-msdosdjgpp/bin/ld: build/debug/librust_lib.a(compiler_builtins-959ba4b0dcda654e.compiler_builtins.25b58a9b9e6e87fe-cgu.1.rcgu.o):compiler_builtins.25b58a9b9e6e87fe-cgu.1:(.text+0xa): undefined reference to `compiler_builtins::math::asinf'
...

[Enet4]

OK, so with this teeny change:

diff --git a/src/coff_go32.rs b/src/coff_go32.rs
index d0bd2d4..1aeb7a4 100644
--- a/src/coff_go32.rs
+++ b/src/coff_go32.rs
@@ -32,13 +32,14 @@ pub const R_386_GOTPC: u32 = 10;
 ///
 /// Link them to the real DJGPP functions instead by renaming the symbols, what could possibly go
 /// wrong
-const FIX_EXTERN_SYMBOLS_PREFIXES: [(&str, &[u8]); 6] = [
+const FIX_EXTERN_SYMBOLS_PREFIXES: [(&str, &[u8]); 7] = [
     ("compiler_builtins::mem::memset", b"memset"),
     ("compiler_builtins::mem::memcmp", b"memcmp"),
     ("compiler_builtins::mem::bcmp", b"bcmp"),
     ("compiler_builtins::mem::strlen", b"strlen"),
     ("compiler_builtins::mem::memcpy", b"memcpy"),
     ("compiler_builtins::mem::memmove", b"memmove"),
+    ("compiler_builtins::math::", b""),
 ];

 pub fn fix_extern_symbol(name: Cow<[u8]>) -> Cow<[u8]> {

I could build my projects successfully using nightly-2024-04-15 as well as the latest nightly, nightly-2024-07-26. Please let me know if you want me to send a PR your way. :)