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Message-ID: <50420942.7090804@iki.fi>
Date: Sat, 01 Sep 2012 16:10:26 +0300
From: Andris Pavenis <andris DOT pavenis AT iki DOT fi>
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To: Juan Manuel Guerrero <juan DOT guerrero AT gmx DOT de>
CC: djgpp AT delorie DOT com
Subject: Re: gcc behaviour if djgpp.env is not available.
References: <201208302244 DOT 31877 DOT juan DOT guerrero AT gmx DOT de>
In-Reply-To: <201208302244.31877.juan.guerrero@gmx.de>
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Reply-To: djgpp AT delorie DOT com

On 30.8.2012 23:44, Juan Manuel Guerrero wrote:
> I do not know if this issue has already been discused but I have noticed
> that the DJGPP port of gcc crashes if it does not find djgpp.env.  If gcc
> needs to load djgpp.env and fails, would not it be better that it issues
> some kind of error message instead of crashing?
> For an user not familiar with DJGPP it would be hard to figure out
> what has gone wrong.
>
> The output below is produced by gcc471b on WinXP after having deleted
> djgpp.env.

Did some debugging (gdb xgcc.exe, command line parameters -B./ 
-print-prog-name=cc1)

The crash is in src/crt0/crt0.S in dos_alloc_ok().


---Type <return> to continue, or q <return> to quit---
    0x00001ba3 <+170>:   sub    $0x1000,%eax
    0x00001ba8 <+175>:   push   %eax
    0x00001ba9 <+176>:   call   0x1d0d <lock_memory>
    0x00001bae <+181>:   mov    %fs:0x18,%eax
    0x00001bb4 <+187>:   mov    %eax,0x17e3e0
    0x00001bb9 <+192>:   mov    %fs:0x10,%eax
    0x00001bbf <+198>:   push   %eax
    0x00001bc0 <+199>:   call   0x1d30 <__sbrk>
    0x00001bc5 <+204>:   cmp    $0xffffffff,%eax
    0x00001bc8 <+207>:   je     0x1c46 <no_memory>
    0x00001bca <+209>:   mov    %eax,0x17ebec
    0x00001bcf <+214>:   mov    %eax,%edi
    0x00001bd1 <+216>:   mov    %fs:0x10,%ecx
    0x00001bd8 <+223>:   shr    $0x2,%ecx
    0x00001bdb <+226>:   xor    %esi,%esi
    0x00001bdd <+228>:   push   %ds
    0x00001bde <+229>:   push   %fs
    0x00001be0 <+231>:   pop    %ds
    0x00001be1 <+232>:   cld
=> 0x00001be2 <+233>:   rep movsl %ds:(%esi),%es:(%edi)
    0x00001be4 <+235>:   pop    %ds
    0x00001be5 <+236>:   mov    0x17e3d8,%eax
    0x00001bea <+241>:   mov    %fs:0x14,%ecx
    0x00001bf1 <+248>:   cmp    %ecx,%eax
    0x00001bf3 <+250>:   jge    0x1bfc <use_stubinfo_stack_size>
    0x00001bf5 <+252>:   mov    %ecx,%eax
    0x00001bf7 <+254>:   mov    %eax,0x17e3d8
End of assembler dump.

(gdb) info reg
eax            0xaa10000        178323456
ecx            0xc58c8cf        207145167
edx            0x3c050000       1006960640
ebx            0x374    884
esp            0x302114 0x302114
ebp            0x158    0x158
esi            0x4000   16384
edi            0xaa14000        178339840
eip            0x1be2   0x1be2 <dos_alloc_ok+233>
eflags         0x13246  [ PF ZF IF #12 #13 RF ]
cs             0x1ef    495
ss             0x1f7    503
ds             0x1e7    487
es             0x1f7    503
fs             0x1e7    487
gs             0x207    519

Checked also with my last build of upcoming gcc-4.8.0 snapshot:

G:\build.gcc\gcc>.\xgcc -v
Using built-in specs.
COLLECT_GCC=g:/build.gcc/gcc/xgcc.exe
Target: djgpp
Configured with: /v204/gcc-4.80-20120825/configure djgpp 
--prefix=/dev/env/DJDIR
  --disable-nls --disable-werror 
--enable-languages=c,c++,fortran,objc,obj-c++,ad
a --enable-libquadmath-support --disable-lto 
--disable-build-poststage1-with-cxx

Thread model: single
gcc version 4.8.0 20120825 (experimental) (GCC)

G:\build.gcc\gcc>set DJGPP=

G:\build.gcc\gcc>.\xgcc -v
xgcc.exe: fatal error: environment variable DJGPP not defined
compilation terminated.

G:\build.gcc\gcc>xgcc -B./ -print-prog-name=cc1
xgcc.exe: fatal error: environment variable DJGPP not defined
compilation terminated.

In this case GCC behaved as it should.  But it is perhaps not the best 
case for comparison (now the GCC 4.8.0 is using C++ not C any more)
Both v2.03 and v2.04 builds of gcc-4.7.1 crashes when DJGPP is not 
defined. Debugging done with v2.04 build.

Andris

>
> F:\x\XZ-50~1.4\_build.204\_build.tmp>gcc  1.c
> Exiting due to signal SIGSEGV
> General Protection Fault at eip=00001be2
> eax=0c720000 ebx=00000299 ecx=0b93d411 edx=3ac30000 esi=00010000 edi=0c730000
> ebp=00000158 esp=00302114 program=C:\DJGPP-2.04\BIN\GCC.EXE
> cs: sel=01a7  base=02990000  limit=3ac2ffff
> ds: sel=017f  base=00008aa0  limit=0000ffff
> es: sel=01af  base=02990000  limit=3ac2ffff
> fs: sel=017f  base=00008aa0  limit=0000ffff
> gs: sel=01bf  base=00000000  limit=0010ffff
> ss: sel=01af  base=02990000  limit=3ac2ffff
> App stack: [00302470..00182470]  Exceptn stack: [00182390..00180450]
>
> Call frame traceback EIPs:
>    0x00001be2
>
>
>
> Regards,
> Juan M. Guerrero
>
>
>