I met a problem when trying to flex abcd.l. I wanted to redirect the output to a new file instead of the default one lex.yy.c
I looked up it in manual finding an option -o(--output=FILE) so I changed my command to flex xx.l -o lex.yy.1.c but error occurs.
flex: can't open --outfile=lex.yy.1.c
/usr/bin/m4:stdin:2621: ERROR: end of file in string
My working environment is cygwin and windows 7
You need to put command line options before positional arguments:
flex -o lex.yy.1.c xx.l
Once a positional (filename) argument is recognized, flex assumes that all following arguments are also filenames. This is the normal form of argument processing for command-line utilities, although some (gcc, for example) allow options to follow the filenames.
(Personally, I'd suggest using a filename like xx.lex.c, but the principle is the same.)
Related
Substrate VM documentation on GitHub (e.g. CONFIGURE.md mentions multiple -H:... options like -H:ReflectionConfigurationResources or -H:ConfigurationFileDirectories. Where can reference documentation of these options be found? GraalVM Reference > Native Image gives just a basic overview.
Output of native-image --help suggests to call native-image --help-extra which suggests to call
native-image --expert-options-all
which prints documented list of options: https://gist.github.com/happylynx/ce642816411ee5c98f04fedd80f4c417.
Currently, there are different levels for the command help:
native-image --help prints default help message with regular options used for generating native image
native-image --help-extra prints help on non-standard options, it shows clearly the usage of the next two options
native-image --expert-options prints help for more advanced options to use by experts
native-image --expert-options-all prints all image building options available, it is clear in the output message that this last command should be used at your own risk
Therefore, you can append a grep expression to one of the four commands above and retrieve the help about a specific command. Here is an example:
native-image --expert-options | grep -A 1 ReflectionConfigurationResources
I am using grep with -A 1 to show one more line in case the first one is truncated
The previous command show the output bellow:
-H:ReflectionConfigurationResources=... Resources describing program elements to be made available for reflection (see ReflectionConfigurationFiles). Default: None
How do you generate ctags only for functions and ignore typedefs and structs?
I've tried ctags --declarations --output=tags program.c, but I have to manually parse this functions.
I've tried: ctags -x --c-kinds=fp path_to_file. 2, but I get the following error:
ctags: unrecognized option '--c-kinds=fp'
Try `ctags --help' for a complete list of options.
Edit:
After I installed exuberant, the following does the trick to get only function headers:
ctags -x --c-types=f ./prog.c
For anyone who stumbles across this question, if you want the entire function (header and body), you'll need to write a script for that. But it's not too hard. I'm using the function headers as, essentially, indices. Just read and find where each function header is in the file to get a unique index - some function names are the same, so iterate over the code and use a while to only add and continue to look in the code for that function until it gets a different index from those in your list of indices. Save the function name and position in a list of tuples and then sort the list in ascending order. Then read the code extracting functions by starting from the top at the first function and reading to the next one in the list. You may have to do some variation of this depending on your situation.
Make sure you are using Exuberant Ctags. On my system:
$ ctags --version
Exuberant Ctags 5.8, Copyright (C) 1996-2009 Darren Hiebert
Compiled: Nov 11 2010, 03:54:52
Addresses: <dhiebert#users.sourceforge.net>, http://ctags.sourceforge.net
Optional compiled features: +wildcards, +regex
Your system must have symbolically linked etags to ctags. When I do so, I replicate your error message. However, the unknown option error using Exuberant Ctags shows as:
ctags: Unknown option: --foo
If you need to generate function declarations from your source, you can easily do it with a little ctags and sed magic:
ctags -x --c-types=f source.c|cut -c51- |sed -e 's/$/;/g' > header.h
I am using a custom build command to run the nasm assembler on a .asm file in my C++ project. I am using %idefs in the assembler code to only compile the code I need. I am checking for the same #defines as in the C++-Code and use define() in Premake 5 to set those, but additionally I need to pass them to nasm on its command line invocation in my Custom Build Command. What I am looking for is a way to concatenate or string replace the Premake internal list of #defines into the command line invocation string of the buildcommands() call. Is there a Premake Token or a way to introspect the lua variables and generate a list from that?
Note that my command line invocation specifically is
buildcommands "nasm.exe -f win32 -o %{cfg.objdir}%{file.basename}.lib %{file.abspath} -DNDEBUG"
Suppose I set defines { "FEAT_A", "FEAT_B" } in my premake5.lua. I then would like to to add -DFEAT_A -DFEAT_B automatically to that build command similar to the -DNDEBUG so I cannot simply insert a simple token. I guess I do have to do something like this (lua pseudo code as I don't really know the syntax):
define_flags = wks.defines.join(" -D")
buildcoommands("nasm.exe [...]"..define_flags)
Do you know if something like this is possible?
How about something like this?
buildcommands('nasm.exe [...] %{table.implode(cfg.defines, "-D", "", " ")} [...]')
In my Informix 4GL program, I have an input field where the user can insert a URL and the feed is later being sent over to the web via a script.
How can I validate the URL at the time of input, to ensure that it's a live link? Can I make a call and see if I get back any errors?
I4GL checking the URL
There is no built-in function to do that (URLs didn't exist when I4GL was invented, amongst other things).
If you can devise a C method to do that, you can arrange to call that method through the C interface. You'll write the method in native C, and then write an I4GL-callable C interface function using the normal rules. When you build the program with I4GL c-code, you'll link the extra C functions too. If you build the program with I4GL-RDS (p-code), you'll need to build a custom runner with the extra function(s) exposed. All of this is standard technique for I4GL.
In general terms, the C interface code you'll need will look vaguely like this:
#include <fglsys.h>
// Standard interface for I4GL-callable C functions
extern int i4gl_validate_url(int nargs);
// Using obsolescent interface functions
int i4gl_validate_url(int nargs)
{
if (nargs != 1)
fgl_fatal(__FILE__, __LINE__, -1318);
char url[4096];
popstring(url, sizeof(url));
int r = validate_url(url); // Your C function
retint(r);
return 1;
}
You can and should check the manuals but that code, using the 'old style' function names, should compile correctly. The code can be called in I4GL like this:
DEFINE url CHAR(256)
DEFINE rc INTEGER
LET url = "http://www.google.com/"
LET rc = i4gl_validate_url(url)
IF rc != 0 THEN
ERROR "Invalid URL"
ELSE
MESSAGE "URL is OK"
END IF
Or along those general lines. Exactly what values you return depends on your decisions about how to return a status from validate_url(). If need so be, you can return multiple values from the interface function (e.g. error number and text of error message). Etc. This is about the simplest possible design for calling some C code to validate a URL from within an I4GL program.
Modern C interface functions
The function names in the interface library were all changed in the mid-00's, though the old names still exist as macros. The old names were:
popstring(char *buffer, int buflen)
retint(int retval)
fgl_fatal(const char *file, int line, int errnum)
You can find the revised documentation at IBM Informix 4GL v7.50.xC3: Publication library in PDF in the 4GL Reference Manual, and you need Appendix C "Using C with IBM Informix 4GL".
The new names start ibm_lib4gl_:
ibm_libi4gl_popMInt()
ibm_libi4gl_popString()
As to the error reporting function, there is one — it exists — but I don't have access to documentation for it any more. It'll be in the fglsys.h header. It takes an error number as one argument; there's the file name and a line number as the other arguments. And it will, presumably, be ibm_lib4gl_… and there'll be probably be Fatal or perhaps fatal (or maybe Err or err) in the rest of the name.
I4GL running a script that checks the URL
Wouldn't it be easier to write a shell script to get the status code? That might work if I can return the status code or any existing results back to the program into a variable? Can I do that?
Quite possibly. If you want the contents of the URL as a string, though, you'll might end up wanting to call C. It is certainly worth thinking about whether calling a shell script from within I4GL is doable. If so, it will be a lot simpler (RUN "script", IIRC, where the literal string would probably be replaced by a built-up string containing the command and the URL). I believe there are file I/O functions in I4GL now, too, so if you can get the script to write a file (trivial), you can read the data from the file without needing custom C. For a long time, you needed custom C to do that.
I just need to validate the URL before storing it into the database. I was thinking about:
#!/bin/bash
read -p "URL to check: " url
if curl --output /dev/null --silent --head --fail "$url"; then
printf '%s\n' "$url exist"
else
printf '%s\n' "$url does not exist"
fi
but I just need the output instead of /dev/null to be into a variable. I believe the only option is to dump the output into a temp file and read from there.
Instead of having I4GL run the code to validate the URL, have I4GL run a script to validate the URL. Use the exit status of the script and dump the output of curl into /dev/null.
FUNCTION check_url(url)
DEFINE url VARCHAR(255)
DEFINE command_line VARCHAR(255)
DEFINE exit_status INTEGER
LET command_line = "check_url ", url
RUN command_line RETURNING exit_status
RETURN exit_status
END FUNCTION {check_url}
Your calling code can analyze exit_status to see whether it worked. A value of 0 indicates success; non-zero indicates a problem of some sort, which can be deemed 'URL does not work'.
Make sure the check_url script (a) exits with status zero on success and non-zero on any sort of failure, and (b) doesn't write anything to standard output (or standard error) by default. The writing to standard error or output will screw up screen layouts, etc, and you do not want that. (You can obviously have options to the script that enable standard output, or you can invoke the script with options to suppress standard output and standard error, or redirect the outputs to /dev/null; however, when used by the I4GL program, it should be silent.)
Your 'script' (check_url) could be as simple as:
#!/bin/bash
exec curl --output /dev/null --silent --head --fail "${1:-http://www.example.com/"
This passes the first argument to curl, or the non-existent example.com URL if no argument is given, and replaces itself with curl, which generates a zero/non-zero exit status as required. You might add 2>/dev/null to the end of the command line to ensure that error messages are not seen. (Note that it will be hell debugging this if anything goes wrong; make sure you've got provision for debugging.)
The exec is a minor optimization; you could omit it with almost no difference in result. (I could devise a scheme that would probably spot the difference; it involves signalling the curl process, though — kill -9 9999 or similar, where the 9999 is the PID of the curl process — and isn't of practical significance.)
Given that the script is just one line of code that invokes another program, it would be possible to embed all that in the I4GL program. However, having an external shell script (or Perl script, or …) has merits of flexibility; you can edit it to log attempts, for example, without changing the I4GL code at all. One more file to distribute, but better flexibility — keep a separate script, even though it could all be embedded in the I4GL.
As Jonathan said "URLs didn't exist when I4GL was invented, amongst other things". What you will find is that the products that have grown to superceed Informix-4gl such as FourJs Genero will cater for new technologies and other things invented after I4GL.
Using FourJs Genero, the code below will do what you are after using the Informix 4gl syntax you are familiar with
IMPORT com
MAIN
-- Should succeed and display 1
DISPLAY validate_url("http://www.google.com")
DISPLAY validate_url("http://www.4js.com/online_documentation/fjs-fgl-manual-html/index.html#c_fgl_nf.html") -- link to some of the features added to I4GL by Genero
-- Should fail and display 0
DISPLAY validate_url("http://www.google.com/testing")
DISPLAY validate_url("http://www.google2.com")
END MAIN
FUNCTION validate_url(url)
DEFINE url STRING
DEFINE req com.HttpRequest
DEFINE resp com.HttpResponse
-- Returns TRUE if http request to a URL returns 200
TRY
LET req = com.HttpRequest.create(url)
CALL req.doRequest()
LET resp = req.getResponse()
IF resp.getStatusCode() = 200 THEN
RETURN TRUE
END IF
-- May want to handle other HTTP status codes
CATCH
-- May want to capture case if not connected to internet etc
END TRY
RETURN FALSE
END FUNCTION
I have embedded lua and I want precompile my script. For that, I call the main of luac (with argc the number of file is 1). My problem is on the function doargs of luac. I don't understand the use of the variable i. Because when I use one script. The result of i after the doargs function is 1. And in the main function we have argc -= i after. And so argc = 0 and I have a error "no file". Any idea ?
luac is meant to be a command line utility for compiling .lua files. This expected usage is the reason why you're getting an error.
When you start an executable the OS passes the name of the program as its first argument (argv[0]). The luac main function assumes it is being called by the OS, so it expects that there will always be at least one argument and its argv[0] will be the name of the executable.
For this reason doargs starts its for loop at 1 and will always ignore that first (0th) argument. It returns how many options it has processed, which is also the offset of the first filename in the argv array. The main function uses this to know where the list of files starts.
If you really want to use the main function to precompile your scripts, then supply an extra dummy argument at the beginning of your argument array and list your files after that. Preferably you should use luac from the command line and supply an output file where the precompiled script will be stored like this:
luac -o outputFile script.lua
Alternatively, take a look at chapter 8 of Programming in Lua (Compilation, Execution, and Errors) for a pure Lua solution, or the the luaL_dofile, luaL_dostring, lua_dump, and lua_load functions in the Reference Manual for a C API solution.