why aren't newlines / other control sequences printed with static_assert? - c++11

int main(int argc, char **argv) {
static_assert(false, R"error(This is an error message. You need to
1. Pick up the phone.
2. Call GhostBusters.
3. Run and hide.
)error");
}
gives
error: static_assert failed "This is an error message. You need to\n\n1. Pick up the phone.\n2. Call GhostBusters.\n3. Run and hide.\n\n"
static_assert(false, err);
^ ~~~~~
1 error generated.
Does anybody know the reason these are "unescaped"? Is it compiler / platform dependent? Part of the standard?

The standard says nothing more than:
the resulting diagnostic message (4.1) shall include the text of the string-literal, if one is supplied, except that characters not in the basic source character set (5.3) are not required to appear in the diagnostic message.
Newlines are part of the basic source character set, so they are required to "appear". Exactly how they appear is not a matter the standard controls.

GCC gives you the newlines you want: https://godbolt.org/g/jS7Sgm
The exact presentation depends on the compiler. Printing escape codes or not can probably best be described as a "quality of implementation" issue.

Related

How to get gcc to compile 16-bit unicode strings

So I'm trying to compile this project : https://github.com/dmitrystu/libusb_stm32 with Segger Embedded studio which uses gcc. The process is choking on this error :
pasting formed 'u"Open source USB stack for STM32"', an invalid preprocessing token
which is caused by this line :
static const struct usb_string_descriptor manuf_desc_en = USB_STRING_DESC("Open source USB stack for STM32");
So USB_STRING_DESC is a macro :
#define USB_STRING_DESC(s) {.bLength = sizeof(CAT(u,s)),.bDescriptorType = USB_DTYPE_STRING,.wString = {CAT(u,s)}}
And CAT is a macro CAT(x,y) x##y. The intent must be to convert a string of type 8-bit char into a 16-bit Unicode type but the compiler doesn't like it. Is there some #include or compiler setting that may be missing that I have to add here? Clearly the author of this code expects it to work so there must be some fault in my setup.
Also I'm not clear on how the sizeof() operation is supposed to work here. As I understand it there is no way to get the length of a string at compile time so that operation will always return the size of a pointer.
In response to Keith's question, the gcc version is 4.2.1. Poking around the compiler settings the default option is the C99 standard, when I changed it to C11 everything compiled just fine. Thanks!

gsdll.init_with_args parameters for Win32 display device

I intent to use gsdll32 to display postscript in a Win32 window (not ghostview).
I need help with the parameters needed by gsdll_init_with_args.
The function immediately returns error -0x12 or -0x100.
I tried several parameter combinations in various sequences:
-sDisplayFormat=16#030804
-dDisplayHandle="1234"
-dDisplayResolution=96
-sDEVICE=display
postscriptfile.ps
As a second question:
What should the parameters be if I want to pipe in the postscript data programmatically ?
Examples would be nice.
Seppe
The supplied source code for Windows uses gs_dll_init_with_args(). If you look in /ghostpdl/psi/dwmain.c, function new_main(int argc, char *argv) then at about line 328 you can see the call happening.
You can follow this through in a debugger to see what the arguments look like (they get sanitised before arriving here). Get it to work the way you want on the command line, then break here with those arguments and you can see what your own code should be providing.
To send the data buffer-by-buffer, we don't have an example. However, you start by calling gsapi_run_string_begin(), then repeatedly calling gsapi_run_string_continue() until you exhaust the data, then call gsapi_run_string_end(). Obviously you will have to check the return code to see if an error occurred.
Finally; please check the AGPL to be sure you can conform to the license restrictions.

Stringify Endpoint for Xcode LLVM Processor Macros

In the "Apple LLVM 7.0 - Preprocessing" section under the "Build Settings" tab, I've defined a Preprocessor Macros as:
STR(arg)=#arg
HUBNAME=STR("myhub")
HUBLISTENACCESS=STR("Endpoint=sb://abc-xyz.servicebus.windows.net/;SharedAccessKeyName=DefaultListenSharedAccessSignature;SharedAccessKey=JKLMNOP=")
In my code, I'm trying to refer to the value of HUBLISTENACCESS as a string:
SBNotificationHub* hub = [[SBNotificationHub alloc] initWithConnectionString:#HUBLISTENACCESS notificationHubPath:#HUBNAME];
But I'm getting errors from Xcode for the initialization of "hub":
Expected ';' at end of declaration
Unterminated function-like macro invocation
Unexpected '#' in program
I suspect that the definition of HUBLISTENACCESS in the Preprocessor Macros needs to be properly escaped but I've tried a few things and can't seem to get it right. Can somebody help me understand what I'm doing wrong?
There's one very obvious reason why you were trying to do failed: you use // in the HUBLISTENACCESS. As in C, things after // were commented out so in the aspect of the compiler, the last line of yours is actually:
HUBLISTENACCESS=STR("Endpoint=sb:
To test it, just remove one slash and it will work again. What you were doing like trying to define things as such:
#define FOO //
which I don't think it's possible. I honestly have no idea how you can do that within the Build Settings, but there are other ways to do it globally via a PCH file (prefix header).
A simple line within the PCH will will save all those troubles:
#define HUBLISTENACCESS #"Endpoint=sb://abc-xyz.servicebus.windows.net/;SharedAccessKeyName=DefaultListenSharedAccessSignature;SharedAccessKey=JKLMNOP="
Then use it as below: (no more # needed!)
NSLog(#"%#", HUBLISTENACCESS);

How do I remove the 'Done' message after my program has executed?

I made a program that is similar to clearing RAM. However, it always leaves a "Done" message followed by a dotted line after being executed. In addition, if you scroll up, you can see that the program was executed. Is there a way to remove both of these things? If you can't hide the fact that a program was executed, could you suppress the 'Done' message?
I have tried adding ClearHome" and " as the last line of my program, and neither stops the Done message from displaying.
Bonus points if your solution can be contained within the original program.
In a separate program, type the following line of code:
AsmPrgmFDCB00AEC9
Then at the end of the original program, type the following line of code:
Asm(prgmPROGRAMNAME
It is recommended that you test this out first with all programs archived, just running the above line of code alone, in case it fails. Hex codes like that one have been known to fail, and sometimes clears the RAM.
You can also try these other hex codes, but always keep in mind the warning above. My RAM has been cleared by this before, so use caution:
http://tibasicdev.wikidot.com/hexcodes
This works on TI 83 and 84, may be different with other calculator types.
EDIT:
I found a way to do this without an external program, and is much simpler.
Just add the following line of code to the end of your program:
Output(1,1," //no space, just a quote
You may or may not have to add ClrHome before that line of code.
This should prevent the Done message from appearing at the end.
Hope this helps!
Put an empty string at the end of your program, so your last line looks like this:
""
Or this
"
The empty string is stored to ans and will be displayed as a blank line rather than the Done message.
There is also an assembly hexcode to do this without leaving the blank line at the top:
FDCB00AEC9
When run at the end of the program using one of the various methods of running assembly, it will leave you with a blank, fully operational homescreen.
Outputting an empty string will prevent the Done message and also preserve Ans, in case a calling program is expecting to use it.
Output(Y,X,"")
See http://tibasicdev.wikidot.com/output for more details on Output(.
In your situation, run Clear Entries (found under Mem), then scroll up so that the Done message is selected and press Clear to get rid of it.

visual c++ operator += is ambiguous

CString szMsg;
//Other non related code
//stOrderInfo.bstrOrderNum is defined as a _bstr_t
szMsg += ", Order: " + stOrderInfo.bstrOrderNum;
I'm converting the above from VS 6.0 to VS2k10 and I'm getting the following error (compiles in VS 6.0):
error C2593: 'operator +=' is ambiguous
What exactly does this mean and how can I fix it?
Because you've hard-coded ", Order: " the compiler is having a hard time to decide which type it should be.
The obvious type should be CString, but it might try to make it to some other string type, and add the number to it.
So it probably can't decide if it's a CString or another string type. So it can't decide what type you're adding to szMsg.
You could just use a type cast:
szMsg += (CString)(", Order: ") + (CString)((char *)(stOrderInfo.bstrOrderNum));
Cast between string types:
How to: Convert Between Various String Types
This means that compiler cannot choose which + operation to use for BSTR + char concatenations. You have a mismatch of three types: CString, _bstr_t, and char.
Try to unify all three operands to a single type, e.g. to CString
The implementation of CString::operator+= is known to have changed in Visual Studio 2010. For example in previous versions it handled embedded null characters OK, just like operator+ keeps doing, but the new version doesn't. So it might be related to this.
EDIT
Link to discussion on this topic:
http://social.msdn.microsoft.com/Forums/en-US/vcmfcatl/thread/c5d7f383-da80-4776-b9b8-a6065839bd87
Better use CString::AppendFormat. But ensure you pass correct format-specifier.

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