C: address of external libc function used as function pointer

• Type: bug (C frontend / external symbol codegen) — Track C
• Status: done
• Owner: Track CA
• Found / Opened: 2026-06-27, M5 sqlite bring-up ([[feature-c-desktop-lua-sqlite-path]]), after function-returning-function- pointer declarations were fixed.
• Closed: 2026-06-27

Symptom

sqlite now advances to:

pascal26:33764: error: @ on external routine not supported; wrap it in a local routine ()

Repro:

./compiler/pascal26 -Ilibrary_candidates/sqlite library_candidates/sqlite/sqlite3.c /tmp/sqlite3

Preprocessed source around the wall:

static void (*unixDlSym(sqlite3_vfs *NotUsed, void *p, const char*zSym))(void){
  void (*(*x)(void*,const char*))(void);
  (void)(NotUsed);
  x = (void(*(*)(void*,const char*))(void))dlsym;
  return (*x)(p, zSym);
}

dlsym is declared from <dlfcn.h> as an external libc import. The C parser represents a bare function name as AN_PROCADDR; x86-64 codegen currently rejects AN_PROCADDR for external routines.

Notes

This is not the same as taking the address of an internal C function. It needs a codegen/linkage strategy for the address of an imported dynamic symbol, or a frontend rewrite that calls the imported routine through a local wrapper when a function pointer value is required.

Fix

IR_PROCADDR now allows external routines on x86-64 by loading the routine's resolved address from the same dynamic GOT slot used by external calls. The new EmitExternalProcAddr helper registers the external if needed and emits mov rax, qword ptr [absolute address], with the address patched through the existing dynamic-call fixup table.

Non-x86-64 targets keep the previous explicit rejection until their backends grow an equivalent address-load sequence.

Regression

Added test/cexternal_func_addr_b106.c, wired into make test-core.

Result

sqlite advances past unixDlSym and now stops at:

pascal26:139609: error: expected C expression ()

The new wall is a block-scope static 2D initializer in sqlite3_complete:

static const u8 trans[8][8] = {
  { 1, 0, 2, 3, 4, 2, 2, 2, },
  ...
};

Filed [[bug-c-local-static-const-multidim-array-init-sqlite]].