b-k / 21st-century-examples Goto Github PK

Hi,
in my understanding, initialization of tally in line 75 of c_factors.c is not C11-compliant:

• if initialized with memset, length of area to set to 0 should be sizeof (_Atomic long int) and not sizeof (long int)
• I bet that initializing an atomic variable with memset gives an undefined behaviour according to C11. I think you should individually initalize each array element with atomic_init

Hi
I met a problem when test string_utilities.c, I ran valgrind and found heap leak. But I was unable to locate and solve the problem.

system info

OS: Ubuntu Mate 17.10
Linux version 4.13.0-21-generic
gcc version 7.2.0
valgrind: 3-13.0

reproduce

compile with
gcc string_utilities.c -g -Wall -std=gnu11 -Dtest_ok_array `pkg-config --cflags glib-2.0` `pkg-config --libs glib-2.0` -o string_utilities

run with
valgrind ./string_utilities

report:
==1096== Memcheck, a memory error detector
==1096== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==1096== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==1096== Command: ./string_utilities
==1096==
OK.
==1096==
==1096== HEAP SUMMARY:
==1096== in use at exit: 18,604 bytes in 6 blocks
==1096== total heap usage: 14 allocs, 8 frees, 19,802 bytes allocated
==1096==
==1096== LEAK SUMMARY:
==1096== definitely lost: 0 bytes in 0 blocks
==1096== indirectly lost: 0 bytes in 0 blocks
==1096== possibly lost: 0 bytes in 0 blocks
==1096== still reachable: 18,604 bytes in 6 blocks
==1096== suppressed: 0 bytes in 0 blocks
==1096== Rerun with --leak-check=full to see details of leaked memory
==1096==
==1096== For counts of detected and suppressed errors, rerun with: -v
==1096== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Hi I am getting the following error when running the example 1.3

/gsl_erf: error while loading shared libraries: libgsl.so.0: cannot open shared object file: No such file or directory

In dict_test.c g_test_trap_fork is used to check that "NULL is not a valid key.\n" is sent to stderr if NULL is used as a lookup key for a dict.

g_test_trap_fork is now deprecated in glib2.0 and so this code no longer compiles. It is recommended to use g_test_trap_subprocess instead.

make dict_test
cc -g -Wall -O3 pkg-config --cflags glib-2.0 -I/usr/include/glib-2.0 dict_test.c dict.o keyval.o -o dict_test
dict_test.c: In function ‘test_failure’:
dict_test.c:47:5: warning: ‘g_test_trap_fork’ is deprecated: Use 'g_test_trap_subprocess' instead [-Wdeprecated-declarations]
if (g_test_trap_fork(0, G_TEST_TRAP_SILENCE_STDOUT | G_TEST_TRAP_SILENCE_STDERR)){
^
In file included from /usr/include/glib-2.0/glib.h:82:0,
from dict_test.c:10:
/usr/include/glib-2.0/glib/gtestutils.h:228:10: note: declared here
gboolean g_test_trap_fork (guint64 usec_timeout,
^
/tmp/cchuUz21.o: In function test_failure': /home/wkmanire/Projects/21st-century-examples/dict_test.c:47: undefined reference tog_test_trap_fork'

Hi,

just found that clang (from XCode and from brew) and gcc (from brew) behaves differently on Example 8-7:

% clang --version
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin16.3.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
% clang constfusion.c -o constfusion
constfusion.c:9:17: warning: initializing 'const int **' with an expression of type 'int **' discards qualifiers in nested pointer types
      [-Wincompatible-pointer-types-discards-qualifiers]
    int const **constptr = &var; // the line that sets up the failure
                ^          ~~~~
1 warning generated.
% ./constfusion
x=20 y=30
% /usr/local/opt/llvm/bin/clang --version
clang version 3.9.0 (tags/RELEASE_390/final)
Target: x86_64-apple-darwin16.3.0
Thread model: posix
InstalledDir: /usr/local/opt/llvm/bin
% /usr/local/opt/llvm/bin/clang constfusion.c -o constfusion
constfusion.c:9:17: warning: initializing 'const int **' with an expression of type 'int **' discards qualifiers in nested pointer types
      [-Wincompatible-pointer-types-discards-qualifiers]
    int const **constptr = &var; // the line that sets up the failure
                ^          ~~~~
1 warning generated.
% ./constfusion
x=20 y=30
% /usr/local/bin/gcc-6 --version
gcc-6 (Homebrew gcc 6.2.0 --without-multilib) 6.2.0
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

% /usr/local/bin/gcc-6 constfusion.c -o constfusion
constfusion.c: In function 'main':
constfusion.c:9:28: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types]
     int const **constptr = &var; // the line that sets up the failure
                            ^
yes@OKEAH:Projects/21st-Century-Examples% ./constfusion
x=30 y=30

So what is the difference in generated code by clang and gcc?

First of all thanks for your book. I'm really liking it. I'm running through your examples using a mac, and there's a number of small mis-matches for example

$ make
C99 -g -O0 -Wall -I/opt/X11/include   stddev_bugged.c   -o stddev_bugged
c99: invalid argument `all' to -W
make: *** [stddev_bugged] Error 64

I've been able to get through most of them, like in this example just not using -Wall, but some examples are harder. Sometimes i'm not sure if it's a platform thing or just my user error. Is it useful/helpful for me to document any of these, or would it be noise to you?

There is a bug on page 190, 2nd edition.
The line:
if(!str)
Should be:
if(!*str)

I also remember another "bug": a semicolon at the end of a one-line-macro, but I do not remember the page.
Regards.

PS:
it's a good book, but some new tips are not so new.
For example, you describe autotools instead of cmake.

Hello,
I started to read your book - it is nice! Thanks for it.
I stuck with gdb, where your examples on page 45 (GDB Variables) do not work for me. maybe I have too new version? (I downgraded gcc, but gdb my distro does not have packaged gdb lower then 7)
In short I cannot use "*x@3" for an array, here is a self explanatory log

[nix-shell:~/Downloads/test]$ gcc --version
gcc (GCC) 5.4.0
[nix-shell:~/Downloads/test]$ gdb --version
GNU gdb (GDB) 7.12.1
[nix-shell:~/Downloads/test]$ cat test.c
int main() {
    int x[20] = {};
    x[0] = 3;
}
[nix-shell:~/Downloads/test]$ gcc -O0 -g -Wall -std=gnu11 test.c
warning about not using x
[nix-shell:~/Downloads/test]$ gdb a.out 
(gdb) b 4
Breakpoint 1 at 0x400530: file test.c, line 4.
(gdb) r
Starting program: /home/kosh/Downloads/test/a.out 

Breakpoint 1, main () at test.c:4
4	}
(gdb) set $ptr=&x[3]
Attempt to take address of value not located in memory.
(gdb) p x
$1 = {3, <optimized out> <repeats 19 times>}
(gdb) p *x
Attempt to take address of value not located in memory.
(gdb) p *x@1
Attempt to take address of value not located in memory.
(gdb) p x[1]
$2 = <optimized out>
(gdb) p x[0]
$3 = 3

Is the problem with new gdb?