Is there a way to write a front-end for my own, invented language?
Let's say I know regular expressions, yacc, lex and stuff, I want only to know how to bind it to existing GCC. I want something like:
%% This is a comment
%% This is source of XD programming language
troll x = 1; %% 'troll' is an automatically guessed type
x+laugh[]; %% Will print some laughs and format the hard drive
Here, the + represents C/C++ structure/class member operator, the square brackets are function call arguments. Semicolon means the same as in C.
How could I bind it so that if i entered
gcc -o app app.troll
it would compile my code, possibly with a similar C intermediate (anyways, the comments would probably be absent):
// The type has been guessed... It's int!!!
int x = 1;
// We can't call a method on an `int`, so we make it an external one
__trollvm_laugh_int (x);
And finally, it would be converted to GENERIC/GIMPLE, optimized and dumped to assembly.
I have seen two approaches:
G++ (GNU C++ Compiler, part of GCC). It compiles directly to GENERIC/GIMPLE
GPC (GNU Pascal Compiler) - translates code to C, then eventually calls GCC
If anyone knows anything, please let me know. Any help appreciated.
Related
I'm currently trying to understand the output of the gcc Vectorizer.
I compiled my program using -O2 -ftree-vectorize -fopt-info-vec-all and gcc 8.2.0.
However, I do not understand, what is meant by some of the output messages, and cannot seem to find explanations on the internet.
What is meant by PHI in the following examples?
test.c:14: note: Analyze phi: i_53 = PHI <i_18(7), 0(5)>
test.c:14: note: Access function of PHI: {1024, +, 4294967295}_2
And what is the problem here?
test.c:5: note: not vectorized: not enough data-refs in basic block.
Any help is greatly appreciated.
(I'm not looking for help in solving the issues atm, just trying to understand what they are in the first place)
As to your first question, Phi or 𝛷 functions are a concept in compiler design. At this stage it appears the compiler is expressing your program in static single assignment form, in which every variable can only be written once, and 𝛷 functions are used to select values from among different variables which may not all exist at a given point in a program.
See https://gcc.gnu.org/onlinedocs/gccint/SSA.html for a gcc-specific description.
I don't know the answer to your second question.
malloc returns a void pointer.so why is it not working for me without typecasting the return value?
The error pretty clear said that gcc is not allowing conversion from void* to int*.
In C, you don't have to cast. In fact it's a bad idea to cast there since it can cause certain subtle errors.
However, casting is required in C++ so that would be my first guess, that you're somehow invoking the C++ compiler. Perhaps your source files are *.cpp or *.C both of which may be auto-magigically treated as C++ rather than C.
See here for more detail:
C++ source files conventionally use one of the suffixes ‘.C’, ‘.cc’, ‘.cpp’, ‘.CPP’, ‘.c++’, ‘.cp’, or ‘.cxx’; C++ header files often use ‘.hh’, ‘.hpp’, ‘.H’, or (for shared template code) ‘.tcc’; and preprocessed C++ files use the suffix ‘.ii’. GCC recognizes files with these names and compiles them as C++ programs even if you call the compiler the same way as for compiling C programs (usually with the name gcc).
The fact that it knows you're trying to convert void* to int* means that you have a valid malloc prototype in place so I can't see it being anything other than the imposition of C++ rules.
Without code I can't help you properly, but you can try this:
p = (int*)malloc(sizeof(int));
Give more info about what you want to do and what you are allocating.
My C++ Library function is int RFD_startBackgroundThread()
My code in the overlay.js is
uri = addon.getResourceURI("components/mac/libReverbFirefoxExtensionLib.dylib");
this.extensionLib = ctypes.open(uri.path);
this.startBackgroundThread = this.extensionLib.declare("RFD_startBackgroundThread", ctypes.default_abi, ctypes.unsigned_int);
The code throws an exception on the last line. It says "Couldn't find function symbol in library".
The library is a "fat dylib binary" combining both i386 and x86_64 (but not PPC arch) on OS X Lion (10.7). Firefox version 11.
Desperately need help.
Thanks.
Rahul.
In most Unix platforms, including OS X, C functions are mapped to symbols just by prefixing with an underscore, so int foo(int) ends up as just _foo.
But that doesn't work for C++, because in C++, you can have two different functions with the same name, in a variety of different ways—you can have int foo(int) and double foo(double), or int MyClass::foo(int), or int foo<int>(int), and so on. So, C++ functions have to be "mangled" to give a unique string. (And then, that unique string is treated like a C function—that is, prefixed with an "_".)
jsctypes knows about knocking off the _, but it can't know how to mangle your function, because you're just giving it a name, not a full prototype. So, you have to figure out in some other way that the mangled name of your function is _Z25RFD_startBackgroundThreadv.
There's no portable standard for how names get mangled. However, the C++ ABI that Apple uses is based on the Itanium C++ API, which requires an API to mangle and demangle C++ functions. Xcode comes with a tool called c++filt that wraps up that API for use at the command line—but it only handles demangling, not mangling. So, it can tell you that _Z25RFD_startBackgroundThreadv means RFD_startBackgroundThread(), but it can't get the other way around.
One way to get the mangled name is to start with nm libfoo.dylib, then use c++filt to check the ones that look like good candidates, until you find one that matches the prototype you're looking for.
Another way is to automate that. Something like this:
nm libfoo.dylib | awk 'NF==2 {printf "%s ",$1; system("c++filt " $2)} NF!=2{print $0}'
… will print the demangled names of all of your symbols.
But probably the best way to go about it is to create a tiny .cpp file that has nothing in it but that one prototype, compile it, and use "otool -SV tiny.a" to see the mangled name.
So, it's not that hard to get the name of the symbol for the C++ function you want to call.
But that doesn't mean you can just call it as if it were a C function. For one pretty obvious example, if you want to call (non-static) Foo::bar(int), you'd better have a valid thing to pass as a "this" pointer, and know how to pass it. See https://bugzilla.mozilla.org/show_bug.cgi?id=505907 for details on what jsctypes in Mozilla can't do, and why.
Well, the problem was, the library does not store the symbol as-is. To see the actual names of the symbols dump the library using nm library-name (optionally redirecting it to a txt file, easier to read).
The symbol in my case was written as __Z25RFD_startBackgroundThreadv. Apparently, I had to know off one underscore and use only _Z25RFD_startBackgroundThreadv.
Thanks to Michael Dautermann!
I'm working on some old source code for an embedded system on an m68k target, and I'm seeing massive memory allocation requests sometimes when calling gcvtf to format a floating point number for display. I can probably work around this by writing my own substitute routine, but the nature of the error has me very curious, because it only occurs when the heap starts at or above a certain address, and it goes away if I hack the .ld linker script or remove any set of global variables (which are placed before the heap in my memory map) that add up to enough byte size so that the heap starts below the mysterious critical address.
So, I thought I'd look in the gcc source code for the compiler version I'm using (m68k-elf-gcc 3.3.2). I downloaded what appears to be the source for this version at http://gcc.petsads.us/releases/gcc-3.3.2/, but I can't find the definition for gcvt or gcvtf anywhere in there. When I search for it, grep only finds some documentation and .h references, but not the definition:
$ find | xargs grep gcvt
./gcc/doc/gcc.info: C library functions `ecvt', `fcvt' and `gcvt'. Given va
lid
./gcc/doc/trouble.texi:library functions #code{ecvt}, #code{fcvt} and #code{gcvt
}. Given valid
./gcc/sys-protos.h:extern char * gcvt(double, int, char *);
So, where is this function actually defined in the source code? Or did I download the entirely wrong thing?
I don't want to change this project to use the most recent gcc, due to project stability and testing considerations, and like I said, I can work around this by writing my own formatting routine, but this behavior is very confusing to me, and it will grind my brain if I don't find out why it's acting so weird.
Wallyk is correct that this is defined in the C library rather than the compiler. However, the GNU C library is (nearly always) only used with Linux compilers and distributions. Your compiler, being a "bare-metal" compiler, almost certainly uses the Newlib C library instead.
The main website for Newlib is here: http://sourceware.org/newlib/, and this particular function is defined in the newlib/libc/stdlib/efgcvt.c file. The sources have been quite stable for a long time, so (unless this is a result of a bug) chances are pretty good that the current sources are not too different from what your compiler is using.
As with the GNU C source, I don't see anything in there that would obviously cause this weirdness that you're seeing, but it's all eventually a bunch of wrappers around the basic sprintf routines.
It is in the GNU C library as glibc/misc/efgcvt.c. To save you some trouble, the code for the function is:
char *
__APPEND (FUNC_PREFIX, gcvt) (value, ndigit, buf)
FLOAT_TYPE value;
int ndigit;
char *buf;
{
sprintf (buf, "%.*" FLOAT_FMT_FLAG "g", MIN (ndigit, NDIGIT_MAX), value);
return buf;
}
The directions for obtain glibc are here.
I am trying to look for definition and declaration of the function nanf() - return 'Not a Number function, which is related to the floating point functionality on Linux gcc compiler environment - (glibc).
I need to use similar/same definition for nanf() on windows to build my code using Visual Studio.
I checked following header files in the Linux src/include folders but did not see anything related to nanf declaration.
/usr/include/math.h
/usr/include/bits/nan.h
Any pointers will be helpful.
thank you,
-AD
The declaration is just (C99 §7.12.11.3):
float nanf(const char *tagp);
or macros that expand to something equivalent. A conformant implementation is highly platform-specific, however, because the standard does not define how to interpret tagp, except to say that the behavior is equivalent to a certain call to strtof, and "The nan functions return a quiet NaN, if available, with content indicated through tagp."
Instead of trying to shoehorn C99 features into the one compiler and library that stubbornly refuses to even try to implement them, why not just use a real C compiler? There are plenty out there.