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GDB and debugging symbols



Try to debug the segment faults of Emacs-cvs buildings I have observed the
following on which I would ask some comment.


When one build the following test case with -g option
----------------------------------------
$ cat hello.c
#include <stdio.h>

int main()
{
    printf("Hello, World!");
    return 0;
}

gcc -g hello.c -o hello
----------------------------------------




then GDB says "no debugging symbols found":
--------------------------------------------
$ gdb ./hello.exe
GNU gdb 6.5.50.20060706-cvs (cygwin-special)
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "i686-pc-cygwin"...(no debugging symbols found)
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(gdb)
--------------------------------------------




Initially I thinked that "no debugging symbols found" did refer GDB 
not hello.exe.

But using the option '-gdwarf-2':
---------------------------------
$ gcc -gdwarf-2 -g3 hello.c -o hello

$ gdb ./hello.exe
GNU gdb 6.5.50.20060706-cvs (cygwin-special)
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "i686-pc-cygwin"...
(gdb)
--------------------------------- 




"no debugging symbols found" disappeared. Besides this
------------------------------------------------------
(gdb) start
Breakpoint 1 at 0x401075: file hello.c, line 4.
Starting program: /tmp/hello.exe
Loaded symbols for /c/WINDOWS/system32/ntdll.dll
Loaded symbols for /c/WINDOWS/system32/kernel32.dll
Loaded symbols for /usr/bin/cygwin1.dll
Loaded symbols for /c/WINDOWS/system32/advapi32.dll
Loaded symbols for /c/WINDOWS/system32/rpcrt4.dll
main () at hello.c:4
4       {
(gdb) info source
Current source file is hello.c
Compilation directory is /tmp/
Located in /tmp/hello.c
Contains 7 lines.
Source language is c.
Compiled with stabs debugging format.
              ^^^^^^^^^^^^^^^^^^^^^^
Does not include preprocessor macro info.
(gdb)
------------------------------------------------------




As you can see compiling with '-gdwarf-2' produces a program for which GDB
says that it was compiled with stabs debugging format, not DWARF 2
debugging format.

This is confirmed even adding '-v':
------------------------------------
$ gcc -v -gdwarf-2 -g3 hello.c -o hello
Reading specs from /usr/lib/gcc/i686-pc-cygwin/3.4.4/specs
Configured with: /usr/build/package/orig/test.new4/gcc-3.4.4-2/configure
--verbo
se --prefix=/usr --exec-prefix=/usr --sysconfdir=/etc --libdir=/usr/lib
--libexe
cdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--enable-languag
es=c,ada,c++,d,f77,pascal,java,objc --enable-nls
--without-included-gettext --en
able-version-specific-runtime-libs --without-x --enable-libgcj
--disable-java-aw
t --with-system-zlib --enable-interpreter --disable-libgcj-debug
--enable-thread
s=posix --enable-java-gc=boehm --disable-win32-registry
--enable-sjlj-exceptions
 --enable-hash-synchronization --enable-libstdcxx-debug
Thread model: posix
gcc version 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)
 /usr/lib/gcc/i686-pc-cygwin/3.4.4/cc1.exe -quiet -v -dD -D__CYGWIN32__
-D__CYGW
IN__ -Dunix -D__unix__ -D__unix -idirafter
/usr/lib/gcc/i686-pc-cygwin/3.4.4/../
../../../include/w32api -idirafter
/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../..
/i686-pc-cygwin/lib/../../include/w32api hello.c -quiet -dumpbase hello.c
-mtune
=pentiumpro -auxbase hello-gdwarf-2 -g3 -version -o
/c/DOCUME~1/Angelo/IMPOST~1/
Temp/cckyExuG.s
ignoring nonexistent directory
"/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i6
86-pc-cygwin/include"
ignoring duplicate directory
"/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686
-pc-cygwin/lib/../../include/w32api"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc/i686-pc-cygwin/3.4.4/include
 /usr/include
 /usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../include/w32api
End of search list.
GNU C version 3.4.4 (cygming special, gdc 0.12, using dmd
0.125) (i686-pc-cygwin
)
        compiled by GNU C version 3.4.4 (cygming special, gdc 0.12, using
dmd 0.
125).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
 /usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/bin/as.exe
-o /c/D
OCUME~1/Angelo/IMPOST~1/Temp/ccktozan.o
/c/DOCUME~1/Angelo/IMPOST~1/Temp/cckyExu
G.s
 /usr/lib/gcc/i686-pc-cygwin/3.4.4/collect2.exe -Bdynamic
--dll-search-prefix=cy
g -o hello.exe /usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../crt0.o
-L/usr/lib/gcc/
i686-pc-cygwin/3.4.4 -L/usr/lib/gcc/i686-pc-cygwin/3.4.4
-L/usr/lib/gcc/i686-pc-
cygwin/3.4.4/../../.. /c/DOCUME~1/Angelo/IMPOST~1/Temp/ccktozan.o -lgcc
-lcygwin
 -luser32 -lkernel32 -ladvapi32 -lshell32 -lgcc
 
$ gdb ./hello.exe
GNU gdb 6.5.50.20060706-cvs (cygwin-special)
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "i686-pc-cygwin"...
(gdb) start
Breakpoint 1 at 0x401075: file hello.c, line 4.
Starting program: /tmp/hello.exe
Loaded symbols for /c/WINDOWS/system32/ntdll.dll
Loaded symbols for /c/WINDOWS/system32/kernel32.dll
Loaded symbols for /usr/bin/cygwin1.dll
Loaded symbols for /c/WINDOWS/system32/advapi32.dll
Loaded symbols for /c/WINDOWS/system32/rpcrt4.dll
main () at hello.c:4
4       {
(gdb) info source
Current source file is hello.c
Compilation directory is /tmp/
Located in /tmp/hello.c
Contains 7 lines.
Source language is c.
Compiled with stabs debugging format.
              ^^^^^^^^^^^^^^^^^^^^^^^
Does not include preprocessor macro info.
(gdb)
------------------------------------


I have all Cygwin installed and updated using the test packages
GCC-3.4.4-2 and bash-3.1-8.


  Angelo.


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