I am having trouble writing a bison parser, and unexpectedly ran into difficulties getting the parser to print debug information. I found two solutions on the web, but neither seems to work.
This advocates to put this code in the main routine:
extern int yydebug;
yydebug = 1;
Unfortunately the C++ compiler detects an undefined reference to `yydebug'.
This suggests putting
#if YYDEBUG == 1
extern yydebug;
yydebug = 1;
#endif
into the grammar file. It compiles but does not produce output.
What does work is to edit the parser file itself, replacing
int yydebug;
by
int yydebug = 1;
The big disadvantage is that I have to redo this every time I change the grammar file, which during debugging would happen constantly. Is there any other way I can provoke the parser into coughing up its secret machinations?
I am using bison v2.4.1 to generate the parser, with the following command-line options:
bison -ldv -p osil -o $(srcdir)/OSParseosil.tab.cpp OSParseosil.y
Although the output is a C++ file, I am using the standard C skeleton.
With bison and the standard C skeleton, to enable debug support you need to do one of the following:
Use the -t (Posix) or --debug (Bison extension) command-line option when you create your grammar. (bison -t ...)
Use the -DYYDEBUG=1 command-line option (gcc or clang, at least) when you compile the generated grammar (gcc -DYYDEBUG=1 parser.tab.c ...`).
Add the %debug directive to your bison source
Put #define YYDEBUG 1 in the prologue in your bison source (the part of the file between %{ and %}.
I'd use -t in the bison command line. It's simple, and since it is Posix standard it probably will also work on other derived parser generators. However, adding %debug to the bison source is also simple; while it is not as portable, it works in bison 2.4.
Once you've done that, simply setting yydebug to a non-zero value is sufficient to produce debug output.
If you want to set yydebug in some translation unit other than the generated parser itself, you need to be aware of the parser prefix you declared in the bison command line. (In the parser itself, yydebug is #defined to the prefixed name.) And you need to declare the debug variable (with the correct prefix) as extern. So in your main, you probably want to use:
extern int osildebug;
// ...
int main(int argc, char** argv) {
osildebug = 1;
// ...
}
If you're using bison, your best place to find information is the bison manual; most of the above answer will be found in that page.
Related
Please check my short code below.
pwrapper.h
#include <stdio.h>
#include <stdarg.h>
extern"C" int mm_printfA(const char *fmt, ...);
extern"C" int mm_printfW(const wchar_t *fmt, ...);
pwrapper.cpp
#include "pwrapper.h"
int mm_printfA(const char *fmt, ...)
{
va_list args;
va_start(args, fmt);
int ret = vprintf(fmt, args);
va_end(args);
return ret;
}
int mm_printfW(const wchar_t *fmt, ...)
{
va_list args;
va_start(args, fmt);
int ret = vwprintf(fmt, args);
va_end(args);
return ret;
}
main.cpp
#include "pwrapper.h"
// cl /MT /D _NO_CRT_STDIO_INLINE main.cpp pwrapper.cpp
void main()
{
mm_printfA("What is %d?\n", 123);
}
#if 0
void usedull()
{
vprintf(NULL, NULL);
vwprintf(NULL, NULL);
}
#endif
For some reason, I need to compile it with _NO_CRT_STDIO_INLINE, like this:
cl /MT /D _NO_CRT_STDIO_INLINE main.cpp pwrapper.cpp
But link stage fails saying unresolved external symbol vwprintf and vprintf .
A very weird workaround I find out is: Enable the usedull() function body -- although never be called, and, link through pwrapper.lib, using bb.bat below:
#setlocal EnableDelayedExpansion
#set CFLAGS=/D _NO_CRT_STDIO_INLINE
cl /nologo /c /MT %CFLAGS% pwrapper.cpp
#if errorlevel 1 exit /b 4
lib /nologo /out:pwrapper.lib pwrapper.obj
#if errorlevel 1 exit /b 4
cl /nologo /c /MT main.cpp
#if errorlevel 1 exit /b 4
link /nologo main.obj pwrapper.lib
#if errorlevel 1 exit /b 4
Well, this really works, but why?
This is not a pleasant workaround, because each exe project needs to include a "useless" usedull() function. So, is there any better way?
I really can't tell why this workaround works, an explanation of it is very welcome.
==== Some Clarification ====
There were two main.cpp in my original post. Let me name them separately for later reference in case someone would bother to answer this weird question.
main.0.cpp refers to the one without usedull().
main.1.cpp refers to the one with usedull().
In this question, I use VC++ headers and libs for application(not for kernel), and
I compile main.0.cpp and main.1.cpp without _NO_CRT_STDIO_INLINE.
I always compile pwrapper.cpp with _NO_CRT_STDIO_INLINE.
Whether having pwrapper.obj go through pwrapper.lib produce the same result in this issue.
In short:
compiling pwrapper.cpp with -D _NO_CRT_STDIO_INLINE tells the compiler you are going to provide your own implementation of vprintf and vwprintf at link time, and
compiling main.cpp without -D _NO_CRT_STDIO_INLINE tells the compiler to include implementations of vprintf and vwprintf which are used at link time to satisfy both the references from usedull and mm_printfA/mm_printfW
so, this particular combination works to resolve all undefined symbols at link time. See below for more discussion however.
Discussion
In stdio.h, vprintf (which I'll focus on, but vwprintf is configured in the same way) is defined like so:
_Check_return_opt_
_CRT_STDIO_INLINE int __CRTDECL vprintf(
_In_z_ _Printf_format_string_ char const* const _Format,
va_list _ArgList
)
#if defined _NO_CRT_STDIO_INLINE
;
#else
{
return _vfprintf_l(stdout, _Format, NULL, _ArgList);
}
#endif
Note that
if _NO_CRT_STDIO_INLINE is defined, this becomes a forward declaration
whereas if it is not defined, the full body is included in the compilation of the including translation unit.
Additionally, in corecrt_stdio_config.h whether _NO_CRT_STDIO_INLINE is defined determines the value of _CRT_STDIO_INLINE; if it is defined, _CRT_STDIO_INLINE is defined as empty, otherwise it is defined as __inline.
Putting these together,
if _NO_CRT_STDIO_INLINE is not defined, these functions will be candidates for inline expansion,
otherwise a separate implementation of that function will need to be provided at link time.
Default Compilation (no /O1, /O2, no _NO_CRT_STDIO_INLINE)
The above works with the specific compile and link invocations you are using, as without optimization the compiler will simply include the function body in the compilation of main.1.obj. You can see this using dumpbin; running dumpbin -symbols main.1.obj | find "| vprintf" prints:
01D 00000000 SECT8 notype () External | vprintf
showing that main.1.obj provides vprintf as an externally available symbol.
Checking pwrapper.obj, we get:
00A 00000000 UNDEF notype () External | vprintf
showing that vprintf is undefined in this object file, and will need to be provided at link time.
Optimisation for Inline Expansion
However, if we change the optimisation option for inline expansion, we get different results. Using even the first level of optimisation (-Ob1, included in -O1 and -O2) like so:
cl -c -Ob1 main.1.cpp
causes the compiler to incorporate the body of vprintf directly into usedull, and remove the separate implementation of vprintf, which can be confirmed using dumpbin. So, as you would now expect, attempting to link main.1.obj and pwrapper.obj together will once again give your original error:
pwrapper.obj : error LNK2019: unresolved external symbol vwprintf referenced in function mm_printfW
pwrapper.obj : error LNK2019: unresolved external symbol vprintf referenced in function mm_printfA
main.exe : fatal error LNK1120: 2 unresolved externals
Multiple Implementations?
So, following on from that it is apparent that compiling both files with -D _NO_CRT_STDIO_INLINE will fail as there will be no implementations of the relevant methods. What about if both are compiled without this definition?
If we check the object files, both have defined symbols for vprintf:
01D 00000000 SECT8 notype () External | vprintf
and:
01A 00000000 SECT7 notype () External | vprintf
which under normal circumstances would result in errors due both to multiple definitions of a symbol and violations of the One Definition Rule. However, when performing inline expansion, the compiler and linker have your back. As per 2:
Rather than expand an inline function defined in a header file, the compiler may create it as a callable function in more than one translation unit. The compiler marks the generated function for the linker to prevent one-definition-rule (ODR) violations.
First question here.
I have some troubles with the XCode Build System, specifically with preprocessor definitions.
I'm trying to define a macro for the objective-c runtime to avoid enforcing the dispatch functions to be cast to an appropriate function pointer type. The usual way to go would be to use #define OBJC_OLD_DISPATCH_PROTOTYPES and then include the header on the next line. Once the header gets included, the macro is already defined and the header is configured accordingly.
But that's where it starts to get weird!
The macro is not recognized at all and the header gets included as if the #define statement was not there so it fails to #define OBJC_OLD_DISPATCH_PROTOTYPES and it gets (re?)defined as 0.
main.c
#include <stdio.h>
#define OBJC_OLD_DISPATCH_PROTOTYPES 1
#include <objc/objc-runtime.h>
int main(int argc, const char * argv[]) {
// From there:
// - Build System: OBJC_OLD_DISPATCH_PROTOTYPES is always 0, except if defined in build settings
// - Clang (only): OBJC_OLD_DISPATCH_PROTOTYPES is 1
printf("%d\n", OBJC_OLD_DISPATCH_PROTOTYPES);
}
The build system acts as expected when the preprocessor macro is defined in the project build settings under the "Apple Clang - Preprocessing" section. It defines the global macro using the -D parameter of clang making it available to any files used by the project.
However, source code compiles correctly when I use clang from a terminal using clang main.c.
Could someone tell me what I need to configure for the build system to behave normally?
It gives a warning when building with Xcode IDE:
Ambiguous expansion of macro 'OBJC_OLD_DISPATCH_PROTOTYPES'
and the output is indeed 0 using Xcode directly, but 1 with clang main.c. The difference is that Xcode uses clang with enabled modules by default: You get the same warning on the command line if you enable modules there:
clang -fmodules main.c
Solution
In Xcode, select the target, go to the "Build Settings" tab and in the "Apple Clang - Language - Modules" section, switch the "Enable Modules (C and Objective-C)" entry to 'NO':
Then you get the expected result in both cases, regardless of whether you use Xcode or Clang on the command line.
Explanation:
If you use modules the following happens:
instead of the preprocessor including the text and compiling the result, a binary representation of the module is used
modules are (independently) precompiled, i.e. they use the definitions from the time the module was precompiled
consequently, preprocess definitions from the code before the include/import statement have no effect on the module (nor on other imported modules).
if modules are enabled, not only #imports are affected, but also #includes are translated into module imports under the hood
So you have a contradictory definitions for the OBJC_OLD_DISPATCH_PROTOTYPES.
The precompiled module uses a 0 for OBJC_OLD_DISPATCH_PROTOTYPES and you redefine it as 1.
BTW: if you use
#define OBJC_OLD_DISPATCH_PROTOTYPES 0
then you use the same definition that the precompiled module is using and therefore there is no warning about an ambiguous expansion of the macro even if modules are enabled.
Without enabled modules, the preprocessor includes the text, compiles the result and returns the expected result, i.e. in objc.h the desired typedef are used.
I'm using QtCreator 4.11.2 , installed via MSYS2, with ClangCodeModel enabled.
Here is my program (this is the result of creating a New Non-QT Plain C Application):
#include <stdio.h>
#include <stdbool.h>
_Bool a;
bool b;
int main()
{
printf("Hello World!\n");
return 0;
}
The .pro file is unchanged from the default:
TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt
SOURCES += \
main.c
The annotation compiler highlights an error saying stdbool.h cannot be found.
But it does not give an error for _Bool a; , so it is clearly running in C99 mode but has some problem with include paths. The "Follow symbol under cursor" option works, opening stdbool.h.
My question is: How do I configure include paths for the annotation compiler or otherwise fix this problem?
I have been unable to figure out how to set options for the annotation compiler or even which compiler binary it is using . Under Tools > Options > C++ > Code Model > Diagnostic Configuration it lets me add -W flags but does not let me add -I flags, a red message pops up saying the option is invalid.
Under Tools > Options > C++ Code Model inspector, there are no diagnostic messages, and the Code Model Inspecting Log shows stdbool.h being correctly found and parsed, as msys64/mingw64/lib/gcc/x86_64-w64-mingw32/9.3.0/include/stdbool.h.
If I disable the ClangCodeModel plugin then there are no errors , but I would like to use the clang version if it can be made to work as in general it has good diagnostics.
The result of clang --version in a shell prompt is:
clang version 10.0.0 (https://github.com/msys2/MINGW-packages.git 3f880aaba91a3d9cdfb222dc270274731a2119a9)
Target: x86_64-w64-windows-gnu
Thread model: posix
InstalledDir: F:\Prog\msys64\mingw64\bin
and if I compile this same source code using clang outside of QtCreator, it compiles and runs correctly with no diagnostics. So the annotation compiler is clearly not the same as the commandline clang?
The Kit I have selected in QtCreator is the autodetected Desktop Qt MinGW-w64 64bit (MSYS2)
The exact same symptoms occur if I make a Plain C++ project and try to include stdbool.h (which is required to exist by the C++ Standard, although deprecated), although interestingly it does accept <cstdbool>.
I have found a workaround of sorts: including in the .pro file the line:
INCLUDEPATH += F:/Prog/msys64/mingw64/lib/gcc/x86_64-w64-mingw32/9.3.0/include/
causes the annotation compiler to work correctly, however this is undesirable as I'd have to keep changing it whenever I switch Kits because it also passes this to the actual build compiler, not just the annotation compiler.
Create file stdbool.h in C:\msys64\mingw64\x86_64-w64-mingw32\include and copy paste this code:
/* Copyright (C) 1998-2017 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/*
* ISO C Standard: 7.16 Boolean type and values <stdbool.h>
*/
#ifndef _STDBOOL_H
#define _STDBOOL_H
#ifndef __cplusplus
#define bool _Bool
#define true 1
#define false 0
#else /* __cplusplus */
/* Supporting _Bool in C++ is a GCC extension. */
#define _Bool bool
#if __cplusplus < 201103L
/* Defining these macros in C++98 is a GCC extension. */
#define bool bool
#define false false
#define true true
#endif
#endif /* __cplusplus */
/* Signal that all the definitions are present. */
#define __bool_true_false_are_defined 1
#endif /* stdbool.h */
Note
Creating a manual file stdbool.h works for me but its a sketchy and a temporary solution for now. Don't use this if you feel its too sketcy. I would rather use a alternative solution than this hack if it exist. This solution might not be good but it still works for me.
After compiling an application with clang 3.6 using -fsanitize=undefined,
I'm trying to start the instrumented program while using a suppression file to ignore some of the errors:
UBSAN_OPTIONS="suppressions=ubsan.supp" ./app.exe
The suppression file ubsan.supp contains:
signed-integer-overflow:example.c
This leads to an error message:
UndefinedBehaviorSanitizer: failed to parse suppressions
The same occurs with a gcc 4.9 build.
The only documentation I can find is http://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html, which is for clang 3.9, while I use 3.6 (which doesn't have documentation for ubsan included).
Can anyone provide working examples for ubsan suppression files, that work in clang 3.6?
Edit: By browsing the source code of ubsan, I found that the only valid suppression type might be "vptr_check" - dunno which version I was looking at though.
Can anyone confirm that in clang 3.9 more suppression types are available?
I didn't spend the time to find out exactly which suppressions were available in clang-3.6, but it appears that in clang-3.7 only vptr_check is available as a suppression. Starting in clang-3.8, the suppressions list is defined to be the list of checks, plus vptr_check.
In clang-3.9 the checks available are:
"undefined"
"null"
"misaligned-pointer-use"
"alignment"
"object-size"
"signed-integer-overflow"
"unsigned-integer-overflow"
"integer-divide-by-zero"
"float-divide-by-zero"
"shift-base"
"shift-exponent"
"bounds"
"unreachable"
"return"
"vla-bound"
"float-cast-overflow"
"bool"
"enum"
"function"
"returns-nonnull-attribute"
"nonnull-attribute"
"vptr"
"cfi"
"vptr_check"
I'd tried it by creating three files, compile.sh, main.cpp and suppressions.supp as shown below. The unsigned-integer-overflow is not a part of undefined that's why it needs to be included specifically. This works on my machine with clang-3.9.
So, I'd guess more suppression types are valid in clang-3.9.
# compile.sh
set -x
UBSAN_OPTIONS=suppressions=suppressions.supp:print_stacktrace=1 #:help=1
export UBSAN_OPTIONS
clang++-3.9 -g -std=c++11 -fsanitize=undefined -fno-omit-frame-pointer -fsanitize=unsigned-integer-overflow main.cpp
./a.out
// main.cpp
#include <bits/stdc++.h>
#include <bits/stl_tree.h>
using namespace std;
int main(int argc, char **argv) {
unsigned int k = UINT_MAX;
k += 1;
return 0;
}
# suppressions.supp
unsigned-integer-overflow:main.cpp
I am using Flex and Bison to create a compiler. As I am trying to create an AST (Abstract Syntax Tree) for my program, I need to port it to C++. So far I have been successful, until a encountered a rather obscure error from my compiler:
Kraken.o: In function Kraken::FlexScanner::FlexScanner()':
Kraken.cc:(.text._ZN6Kraken11FlexScannerC2Ev[_ZN6Kraken11FlexScannerC5Ev]+0x26): undefined reference to vtable for Kraken::FlexScanner'
Kraken.o: In function Kraken::FlexScanner::~FlexScanner()':
Kraken.cc:(.text._ZN6Kraken11FlexScannerD2Ev[_ZN6Kraken11FlexScannerD5Ev]+0xb): undefined reference to vtable for Kraken::FlexScanner'
Here is all the relevant code:
Kraken.cc:
#include "KrakenScanner.hh"
#include "KrakenParser.hh"
int main(int argc, char * argv[]) {
Kraken::Parser parser;
return parser.parse();
}
KrakenScanner.hh:
#ifndef KRAKENSCANNER_HH_
#define KRAKENSCANNER_HH_
#if ! defined(yyFlexLexerOnce)
#include <FlexLexer.h>
#endif
#undef YY_DECL
#define YY_DECL int Kraken::FlexScanner::yylex()
#include "parser.hh"
namespace Kraken {
class FlexScanner : public yyFlexLexer {
public:
int yylex(Kraken::BisonParser::semantic_type* lval);
private:
int yylex();
Kraken::BisonParser::semantic_type* yylval;
};
}
#endif /* KRAKENSCANNER_HH_ */
KrakenScanner.cc:
#include "KrakenScanner.hh"
int Kraken::FlexScanner::yylex(Kraken::BisonParser::semantic_type* lval) {
yylval = lval; return yylex();
}
Makefile:
OBJS := Kraken.o parser.o scanner.o KrakenScanner.o KrakenParser.o
%.cc: %.y
bison -o $(#:%.o=%.d) $<
%.cc: %.l
flex -o$(#:%.o=%.d) -i $<
all: $(OBJS)
g++ -okraken $(OBJS)
Kraken.o: Kraken.cc KrakenScanner.o KrakenParser.o
KrakenScanner.o: KrakenScanner.hh KrakenScanner.cc parser.o
parser.o: parser.hh parser.cc
parser.cc: parser.y
scanner.o: scanner.cc
scanner.cc: scanner.l
KrakenParser.o: KrakenParser.hh KrakenParser.cc KrakenScanner.o`
I don't know if this will help, but FlexLexer.h defines the classes FlexLexer and yyFlexLexer. FlexLexer declares just a virtual destructor, and yyFlexLexer defines both a constructor and destructor. Also, when I attempt to overload the constr. and destr. in Kraken.cc, I get an error saying that the two are "implicitly defined".
Try a clean rebuild (rm *.o) and recompile. The compiler is supposed to generate this stuff automatically. Some compilers have special non-portable magic to influence v-table linking, but I don't see anything like that in your code.
Also, I see in your makefile that you've written a rule for linking with g++, but you haven't written any rule for compilation. So make is using its built-in rules, which might by the C++ compiler provided by your OS, not g++.
Another thing is that makefile rules should put the primary source first. For example:
wrong:
KrakenScanner.o: KrakenScanner.hh KrakenScanner.cc parser.o
right:
KrakenScanner.o: KrakenScanner.cc KrakenScanner.hh
Finally, object files aren't used to build other object files, only during linking.
First off, that error message is from your linker, not your compiler. It looks like you aren't linking in KrakenScanner.o. It also helps to apply the name demangler for your compiler to your compiler/linker error output.
What compiler are you using?