DOS ain't dead - trip report: Tiny C Compiler 0.9.27

trip report: Tiny C Compiler 0.9.27 (Miscellaneous)

posted by tkchia , 05.02.2026, 16:44

Hello bencollver,

> I believe the disassembly corresponds to the for(;;) loop body, probably at
> "sym->next = last_sym". I am not sure i am ready to debug this one.

__sym_malloc seems to be used to extend a pool of free struct Sym thingies (TCC can then allocate new struct Sym objects from this free pool). It is odd that the routine is crashing.

Anyway, here is the machine code output that I got for this routine after compiling tccgen.c on my end (on a Linux machine):

00000a18 <__sym_malloc>: a18: 55 push %ebp a19: 89 e5 mov %esp,%ebp a1b: 81 ec 10 00 00 00 sub $0x10,%esp a21: b8 ec 1f 00 00 mov $0x1fec,%eax a26: 50 push %eax a27: e8 fc ff ff ff call a28 <__sym_malloc+0x10> a28: R_386_PC32 tcc_malloc a2c: 83 c4 04 add $0x4,%esp a2f: 89 45 fc mov %eax,-0x4(%ebp) a32: 8b 45 fc mov -0x4(%ebp),%eax a35: 50 push %eax a36: b8 00 00 00 00 mov $0x0,%eax a37: R_386_32 nb_sym_pools a3b: 50 push %eax a3c: b8 00 00 00 00 mov $0x0,%eax a3d: R_386_32 sym_pools a41: 50 push %eax a42: e8 fc ff ff ff call a43 <__sym_malloc+0x2b> a43: R_386_PC32 dynarray_add a47: 83 c4 0c add $0xc,%esp a4a: 8b 05 00 00 00 00 mov 0x0,%eax a4c: R_386_32 sym_free_first a50: 89 45 f4 mov %eax,-0xc(%ebp) a53: 8b 45 fc mov -0x4(%ebp),%eax a56: 89 45 f8 mov %eax,-0x8(%ebp) a59: b8 00 00 00 00 mov $0x0,%eax a5e: 89 45 f0 mov %eax,-0x10(%ebp) a61: 8b 45 f0 mov -0x10(%ebp),%eax a64: 81 f8 e3 00 00 00 cmp $0xe3,%eax a6a: 0f 83 2e 00 00 00 jae a9e <__sym_malloc+0x86> a70: e9 0b 00 00 00 jmp a80 <__sym_malloc+0x68> a75: 8b 45 f0 mov -0x10(%ebp),%eax a78: 89 c1 mov %eax,%ecx a7a: 40 inc %eax a7b: 89 45 f0 mov %eax,-0x10(%ebp) a7e: eb e1 jmp a61 <__sym_malloc+0x49> a80: 8b 45 f8 mov -0x8(%ebp),%eax a83: 83 c0 18 add $0x18,%eax a86: 8b 4d f4 mov -0xc(%ebp),%ecx a89: 89 08 mov %ecx,(%eax) a8b: 8b 45 f8 mov -0x8(%ebp),%eax a8e: 89 45 f4 mov %eax,-0xc(%ebp) a91: 8b 45 f8 mov -0x8(%ebp),%eax a94: 89 c1 mov %eax,%ecx a96: 83 c0 24 add $0x24,%eax a99: 89 45 f8 mov %eax,-0x8(%ebp) a9c: eb d7 jmp a75 <__sym_malloc+0x5d> a9e: 8b 45 f4 mov -0xc(%ebp),%eax aa1: 89 05 00 00 00 00 mov %eax,0x0 aa3: R_386_32 sym_free_first aa7: 8b 45 f4 mov -0xc(%ebp),%eax aaa: c9 leave aab: c3 ret

(The R_386_PC32 and R_386_32 are ELF relocations.) If the compiler output something different on your end -- modulo different instruction encodings -- then it might be a case of miscompilation.

Thank you!

---
https://codeberg.org/tkchia · https://disroot.org/tkchia · 😴 "MOV AX,0D500H+CMOS_REG_D+NMI"

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Complete thread:

trip report: Tiny C Compiler 0.9.27 - bencollver, 04.02.2026, 17:02 (Miscellaneous)
- trip report: Tiny C Compiler 0.9.27 - tkchia, 04.02.2026, 17:55
  - trip report: Tiny C Compiler 0.9.27 - bencollver, 04.02.2026, 18:48
    - trip report: Tiny C Compiler 0.9.27 - Japheth, 04.02.2026, 21:12
      - trip report: Tiny C Compiler 0.9.27 - bencollver, 04.02.2026, 21:44
      - trip report: Tiny C Compiler 0.9.27 - bretjohn, 05.02.2026, 22:24
        trip report: Tiny C Compiler 0.9.27 - Rugxulo, 05.02.2026, 23:09
        trip report: Tiny C Compiler 0.9.27 - bretjohn, 06.02.2026, 01:59
    - trip report: Tiny C Compiler 0.9.27 - bencollver, 04.02.2026, 21:38
      - trip report: Tiny C Compiler 0.9.27 - tkchia, 05.02.2026, 16:44
        trip report: Tiny C Compiler 0.9.27 - bencollver, 05.02.2026, 18:34
        trip report: Tiny C Compiler 0.9.27 - bencollver, 05.02.2026, 22:22
        trip report: Tiny C Compiler 0.9.27 - tkchia, 05.02.2026, 23:13
        trip report: Tiny C Compiler 0.9.27 - Rugxulo, 05.02.2026, 23:16
        trip report: Tiny C Compiler 0.9.27 - tkchia, 05.02.2026, 23:18
        trip report: Tiny C Compiler 0.9.27 - tkchia, 06.02.2026, 23:45
- trip report: Tiny C Compiler 0.9.27 - bencollver, 11.02.2026, 00:44
  - trip report: Tiny C Compiler 0.9.27 - Rugxulo, 11.02.2026, 01:42
    - trip report: Tiny C Compiler 0.9.27 - bencollver, 11.02.2026, 02:06