I don't understand why freertos do not allow to change extern variables
(myData)
here is my poject
file main.c
uint16_t Mydata = 0;
main()
{
System_Init();
xTaskCreate(Task1, (const char*)"Task1", 100, NULL, 4, NULL);
xTaskCreate(Task2, (const char*)"Task2", 100, NULL, 3, NULL);
vTaskStartScheduler();
}
file Task1.c
extern uint16_t Mydata;
void Task1(void *p)
{
while(1)
{
vTaskDelay(10);
printf("Result: %d", Mydata);
}
}
file Task2.c
extern uint16_t Mydata;
void Task2(void *p)
{
while(1)
{
Mydata++;
vTaskDelay(10);
}
}
but the result is never correct
most of result is like "13842930", "-18234952", or something like that !
can anyone tell me why?
(I'm sorry because of my bad English)
thank for your help !
You cannot use %d for printing a value of uint16_t. %d expects an int. You either have to cast your value to int in the printf() call (printf("Result: %d", (int)Mydata);), or use proper specifier (printf("Result: %" PRIu16 "", Mydata);). The second solution might not be supported by your toolchain.
http://en.cppreference.com/w/cpp/io/c/fprintf
Your variable should be declared volatile, otherwise compiler may as well read it once an never update the value from RAM.
Related
I am creating a currency converter Win32 program in Embarcadero C++Builder. I wrote a function for transforming date from format specified on user PC to YYYY-MM-DD format. I need that part because of API settings.
When I have this function inside my project it works fine, but I need to have that function inside a DLL.
This is how my code looks like:
#pragma hdrstop
#pragma argsused
#include <SysUtils.hpp>
extern DELPHI_PACKAGE void __fastcall DecodeDate(const System::TDateTime DateTime, System::Word &Year, System::Word &Month, System::Word &Day);
extern "C" UnicodeString __declspec (dllexport) __stdcall datum(TDateTime dat) {
Word dan, mjesec, godina;
UnicodeString datum, datum_dan, datum_mjesec, datum_godina;
DecodeDate(dat, godina, mjesec, dan);
if (dan<=9 && mjesec<=9) {
datum_dan="0"+IntToStr(dan);
datum_mjesec="0"+IntToStr(mjesec);
}
if (dan<=9 && mjesec>9) {
datum_dan="0"+IntToStr(dan);
datum_mjesec=IntToStr(mjesec);
}
if (dan>9 && mjesec<=9) {
datum_dan=IntToStr(dan);
datum_mjesec="0"+IntToStr(mjesec);
}
if (dan>9 && mjesec>9) {
datum_dan=IntToStr(dan);
datum_mjesec=IntToStr(mjesec);
}
datum_godina=IntToStr(godina);
return datum_godina+"-"+datum_mjesec+"-"+datum_dan;
}
extern "C" int _libmain(unsigned long reason)
{
return 1;
}
`
I've included SysUtils.hpp and declared DecodeDate() function, without those lines I have a million errors. But with code looking like this, I am getting this error, which I can't get rid of:
[bcc32 Error] File1.cpp(30): E2015 Ambiguity between '_fastcall System::Sysutils::DecodeDate(const System::TDateTime,unsigned short &,unsigned short &,unsigned short &) at c:\program files (x86)\embarcadero\studio\19.0\include\windows\rtl\System.SysUtils.hpp:3466' and '_fastcall DecodeDate(const System::TDateTime,unsigned short &,unsigned short &,unsigned short &) at File1.cpp:25'
Full parser context
File1.cpp(27): parsing: System::UnicodeString __stdcall datum(System::TDateTime)
Can you help me to get rid of that error?
The error message is self-explanatory. You have two functions with the same name in scope, and the compiler doesn't know which one you want to use on line 30 because the parameters you are passing in satisfy both function declarations.
To fix the error, you can change this line:
DecodeDate(dat, godina, mjesec, dan);
To either this:
System::Sysutils::DecodeDate(dat, godina, mjesec, dan);
Or this:
dat.DecodeDate(&godina, &mjesec, &dan);
However, either way, you should get rid of your extern declaration for DecodeDate(), as it doesn't belong in this code at all. You are not implementing DecodeDate() yourself, you are just using the one provided by the RTL. There is already a declaration for DecodeDate() in SysUtils.hpp, which you are #include'ing in your code. That is all the compiler needs.
Just make sure you are linking to the RTL/VCL libraries to resolve the function during the linker stage after compiling. You should have enabled VCL support when you created the DLL project. If you didn't, recreate your project and enable it.
BTW, there is a MUCH easier way to implement your function logic - instead of manually pulling apart the TDateTime and reconstituting its components, just use the SysUtils::FormatDateTime() function or the TDateTime::FormatString() method instead, eg:
UnicodeString __stdcall datum(TDateTime dat)
{
return FormatDateTime(_D("yyyy'-'mm'-'dd"), dat);
}
UnicodeString __stdcall datum(TDateTime dat)
{
return dat.FormatString(_D("yyyy'-'mm'-'dd"));
}
That being said, this code is still wrong, because it is not safe to pass non-POD types, like UnicodeString, over the DLL boundary like you are doing. You need to re-think your DLL function design to use only interop-safe POD types. In this case, change your function to either:
take a wchar_t* as input from the caller, and just fill in the memory block with the desired characters. Let the caller allocate the actual buffer and pass it in to your DLL for populating:
#pragma hdrstop
#pragma argsused
#include <SysUtils.hpp>
extern "C" __declspec(dllexport) int __stdcall datum(double dat, wchar_t *buffer, int buflen)
{
UnicodeString s = FormatDateTime(_D("yyyy'-'mm'-'dd"), dat);
if (!buffer) return s.Length() + 1;
StrLCopy(buffer, s.c_str(), buflen-1);
return StrLen(buffer);
}
extern "C" int _libmain(unsigned long reason)
{
return 1;
}
wchar_t buffer[12] = {};
datum(SomeDateValueHere, buffer, 12);
// use buffer as needed...
int len = datum(SomeDateValueHere, NULL, 0);
wchar_t *buffer = new wchar_t[len];
int len = datum(SomeDateValueHere, buffer, len);
// use buffer as needed...
delete[] buffer;
allocate a wchar_t[] buffer to hold the desired characters, and then return a wchar_t* pointer to that buffer to the caller. Then export a second function that the caller can pass the returned wchar_t* back to you so you can free it correctly.
#pragma hdrstop
#pragma argsused
#include <SysUtils.hpp>
extern "C" __declspec(dllexport) wchar_t* __stdcall datum(double dat)
{
UnicodeString s = FormatDateTime("yyyy'-'mm'-'dd", dat);
wchar_t* buffer = new wchar_t[s.Length()+1];
StrLCopy(buffer, s.c_str(), s.Length());
return buffer;
}
extern "C" __declspec(dllexport) void __stdcall free_datum(wchar_t *dat)
{
delete[] dat;
}
extern "C" int _libmain(unsigned long reason)
{
return 1;
}
wchar_t *buffer = datum(SomeDateValueHere);
// use buffer as needed...
free_datum(buffer);
I'd like a step by step explanation on how to parse the arguments of a variadic function
so that when calling va_arg(ap, TYPE); I pass the correct data TYPE of the argument being passed.
Currently I'm trying to code printf.
I am only looking for an explanation preferably with simple examples but not the solution to printf since I want to solve it myself.
Here are three examples which look like what I am looking for:
https://stackoverflow.com/a/1689228/3206885
https://stackoverflow.com/a/5551632/3206885
https://stackoverflow.com/a/1722238/3206885
I know the basics of what typedef, struct, enum and union do but can't figure out some practical application cases like the examples in the links.
What do they really mean? I can't wrap my brain around how they work.
How can I pass the data type from a union to va_arg like in the links examples? How does it match?
with a modifier like %d, %i ... or the data type of a parameter?
Here's what I've got so far:
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include "my.h"
typedef struct s_flist
{
char c;
(*f)();
} t_flist;
int my_printf(char *format, ...)
{
va_list ap;
int i;
int j;
int result;
int arg_count;
char *cur_arg = format;
char *types;
t_flist flist[] =
{
{ 's', &my_putstr },
{ 'i', &my_put_nbr },
{ 'd', &my_put_nbr }
};
i = 0;
result = 0;
types = (char*)malloc( sizeof(*format) * (my_strlen(format) / 2 + 1) );
fparser(types, format);
arg_count = my_strlen(types);
while (format[i])
{
if (format[i] == '%' && format[i + 1])
{
i++;
if (format[i] == '%')
result += my_putchar(format[i]);
else
{
j = 0;
va_start(ap, format);
while (flist[j].c)
{
if (format[i] == flist[j].c)
result += flist[i].f(va_arg(ap, flist[i].DATA_TYPE??));
j++;
}
}
}
result += my_putchar(format[i]);
i++;
}
va_end(ap);
return (result);
}
char *fparser(char *types, char *str)
{
int i;
int j;
i = 0;
j = 0;
while (str[i])
{
if (str[i] == '%' && str[i + 1] &&
str[i + 1] != '%' && str[i + 1] != ' ')
{
i++;
types[j] = str[i];
j++;
}
i++;
}
types[j] = '\0';
return (types);
}
You can't get actual type information from va_list. You can get what you're looking for from format. What it seems you're not expecting is: none of the arguments know what the actual types are, but format represents the caller's idea of what the types should be. (Perhaps a further hint: what would the actual printf do if a caller gave it format specifiers that didn't match the varargs passed in? Would it notice?)
Your code would have to parse the format string for "%" format specifiers, and use those specifiers to branch into reading the va_list with specific hardcoded types. For example, (pseudocode) if (fspec was "%s") { char* str = va_arg(ap, char*); print out str; }. Not giving more detail because you explicitly said you didn't want a complete solution.
You will never have a type as a piece of runtime data that you can pass to va_arg as a value. The second argument to va_arg must be a literal, hardcoded specification referring to a known type at compile time. (Note that va_arg is a macro that gets expanded at compile time, not a function that gets executed at runtime - you couldn't have a function taking a type as an argument.)
A couple of your links suggest keeping track of types via an enum, but this is only for the benefit of your own code being able to branch based on that information; it is still not something that can be passed to va_arg. You have to have separate pieces of code saying literally va_arg(ap, int) and va_arg(ap, char*) so there's no way to avoid a switch or a chain of ifs.
The solution you want to make, using the unions and structs, would start from something like this:
typedef union {
int i;
char *s;
} PRINTABLE_THING;
int print_integer(PRINTABLE_THING pt) {
// format and print pt.i
}
int print_string(PRINTABLE_THING pt) {
// format and print pt.s
}
The two specialized functions would work fine on their own by taking explicit int or char* params; the reason we make the union is to enable the functions to formally take the same type of parameter, so that they have the same signature, so that we can define a single type that means pointer to that kind of function:
typedef int (*print_printable_thing)(PRINTABLE_THING);
Now your code can have an array of function pointers of type print_printable_thing, or an array of structs that have print_printable_thing as one of the structs' fields:
typedef struct {
char format_char;
print_printable_thing printing_function;
} FORMAT_CHAR_AND_PRINTING_FUNCTION_PAIRING;
FORMAT_CHAR_AND_PRINTING_FUNCTION_PAIRING formatters[] = {
{ 'd', print_integer },
{ 's', print_string }
};
int formatter_count = sizeof(formatters) / sizeof(FORMAT_CHAR_AND_PRINTING_FUNCTION_PAIRING);
(Yes, the names are all intentionally super verbose. You'd probably want shorter ones in the real program, or even anonymous types where appropriate.)
Now you can use that array to select the correct formatter at runtime:
for (int i = 0; i < formatter_count; i++)
if (current_format_char == formatters[i].format_char)
result += formatters[i].printing_function(current_printable_thing);
But the process of getting the correct thing into current_printable_thing is still going to involve branching to get to a va_arg(ap, ...) with the correct hardcoded type. Once you've written it, you may find yourself deciding that you didn't actually need the union nor the array of structs.
I have a string in a uint8_t str[] array and I am trying to store the positions of characters within the str in another variable called uint8_t pos[]. The code is written in Code Composer Studio vs 5.4
I tried using sprintf(), type casting as well as changing the type of uint8_t pos[] to int pos[] as well as unsigned int pos[]. None of these work.
The code breaks at the sprintf statement and comes to a halt by reaching an undefined memory location. When I run in assembly after reaching sprintf statement, it gives an error saying that a source code for sprint.c cannot be found in location.
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include "tm4c123gh6pm.h"
#include <stdio.h>
void initHw()
{
.
.
}
int main(void)
{
// Initialize hardware
initHw();
char strRx[80];
int count =0;
int count_enter=0;
uint8_t posStr[80];
uint8_t typeStr[80];
int pos=0;
int len;
unsigned int j=0, argCount=0;
while(1)
{
if(count == 0)
{
putsUart0("Enter characters for the string\r\n");
}
if(count <= 80)
{
char c = getcUart0();
if(c=='\b')
if(count>0)
count--;
else
break;
if(c>=' ')
{
strRx[count]=c;
count++;
}
if(count==80 || c==13)//'\r')
{
count_enter++;
if(count_enter==1) //count==80 before carriage return
{
len = count;
strRx[count]='\0';
while(count!=80)
strRx[count++]='\0';
count_enter=0;
putsUart0("\r\nEntered string is:\r\n");
putsUart0(strRx);
putsUart0("\r\n");
}
j=0;
//char a[10];
for(pos=0; pos!=len; pos++)// strRx[pos]!='\0'; pos++)
{
char a[80];
if((strRx[pos]>='A' && strRx[pos]<='Z') || (strRx[pos]>='a' && strRx[pos]<='z'))
{
typeStr[j]='a';
//posStr[j]=pos;
a[j]=pos;
sprintf(a,"%u",pos); //source not found
//a[j]=pos;
//posStr[j]=sprintf("%c",a);
//posStr[j]=(uint8_t)a;//a;
while(strRx[pos]!='\0'&&((strRx[pos]>='A' && strRx[pos]<='Z') || (strRx[pos]>='a' && strRx[pos]<='z')))
{
pos++;
}
pos--;
j++;
}
else if(strRx[pos]>='0' && strRx[pos]<='9')
{
typeStr[j]='n';
a[j]=pos;
sprintf(a,"%u",pos);
//posStr[j]=pos;//a;
while(strRx[pos]!='\0'&&((strRx[pos]>='0' && strRx[pos]<='9')))
{
pos++;
}
pos--;
j++;
}
else
{
while(strRx[pos]!='\0'&&((strRx[pos]<'A' && strRx[pos]>'Z') && (strRx[pos]<'a' && strRx[pos]>'z') && (strRx[pos+1]<'0' && strRx[pos+1]>'9')))
pos++;
}
}
argCount=j;
while(j!=80)
{
typeStr[j++]='\0';
posStr[j++]='\0';
}
count = 0;
}//if(count==80 || c==13)//'\r')
}//if count<=80
}//while(1)
}//main
The "unable to locate sprintf.c" error probably just means that the debugger cannot locate the source file, which means it cannot show the source code in the debugger window. It's possible that you don't have the source code for sprintf.c and all you have is the precompiled library. Or maybe you do have the source code and the debugger is simply looking in the wrong path. If you have the source code then there may be a way to tell the debugger which path to find it.
But that is just a debugger display issue -- It is not what is causing your program to crash. The problem may be in your code but you'd have to share your code for us to identify that. Or the problem may be a couple other issues that can occur with the printf related routines.
1) printf routines can use a relatively large amount of stack space. So check for a stack overflow and increase the stack size if necessary.
2) Some embedded libraries provide multiple implementations of the printf routines such as "small", "no-float", and "full". The limited implementations use less code space but don't support all of the format specifiers. So make sure the implementation of sprintf that you've linked with supports all the format specifiers that you're actually using. Look through the project settings under linker or libraries for an option to select which version of printf is used.
Given I have a type specifier as returned by method_copyReturnType(). In the GNU runtime delivered with the GCC there are various methods to work with such a type specifier like objc_sizeof_type(), objc_alignof_type() and others.
When using the Apple runtime there are no such methods.
How can I interpret a type specifier string (e.g. get the size of a type) using the Apple runtime without implementing an if/else or case switch for myself?
[update]
I am not able to use the Apple Foundation.
I believe that you're looking for NSGetSizeAndAlignment:
Obtains the actual size and the aligned size of an encoded type.
const char * NSGetSizeAndAlignment (
const char *typePtr,
NSUInteger *sizep,
NSUInteger *alignp
);
Discussion
Obtains the actual size and the aligned size of the first data type represented by typePtr and returns a pointer to the position of the next data type in typePtr.
This is a Foundation function, not part of the base runtime, which is probably why you didn't find it.
UPDATE: Although you didn't initially mention that you're using Cocotron, it is also available there. You can find it in Cocotron's Foundation, in NSObjCRuntime.m.
Obviously, this is much better than rolling your own, since you can trust it to always correctly handle strings generated by its own runtime in the unlikely event that the encoding characters should change.
For some reason, however, it's unable to handle the digit elements of a method signature string (which presumably have something to do with offsets in memory). This improved version, by Mike Ash will do so:
static const char *SizeAndAlignment(const char *str, NSUInteger *sizep, NSUInteger *alignp, int *len)
{
const char *out = NSGetSizeAndAlignment(str, sizep, alignp);
if(len)
*len = out - str;
while(isdigit(*out))
out++;
return out;
}
afaik, you'll need to bake that info into your binary. just create a function which returns the sizeof and alignof in a struct, supports the types you must support, then call that function (or class method) for the info.
The program below shows you that many of the primitives are just one character. So the bulk of the function's implementation could be a switch.
static void test(SEL sel) {
Method method = class_getInstanceMethod([NSString class], sel);
const char* const type = method_copyReturnType(method);
printf("%s : %s\n", NSStringFromSelector(sel).UTF8String, type);
free((void*)type);
}
int main(int argc, char *argv[]) {
#autoreleasepool {
test(#selector(init));
test(#selector(superclass));
test(#selector(isEqual:));
test(#selector(length));
return 0;
}
}
and you could then use this as a starting point:
typedef struct t_pair_alignof_sizeof {
size_t align;
size_t size;
} t_pair_alignof_sizeof;
static t_pair_alignof_sizeof MakeAlignOfSizeOf(size_t align, size_t size) {
t_pair_alignof_sizeof ret = {align, size};
return ret;
}
static t_pair_alignof_sizeof test2(SEL sel) {
Method method = class_getInstanceMethod([NSString class], sel);
const char* const type = method_copyReturnType(method);
const size_t length = strlen(type);
if (1U == length) {
switch (type[0]) {
case '#' :
return MakeAlignOfSizeOf(__alignof__(id), sizeof(id));
case '#' :
return MakeAlignOfSizeOf(__alignof__(Class), sizeof(Class));
case 'c' :
return MakeAlignOfSizeOf(__alignof__(signed char), sizeof(signed char));
...
When will the _vsnprintf crash?
I use it like this:
void My_Printf(const char *szFormatString, ...)
{
va_list my_args;
va_start(my_args, szFormatString);
AppendToLog(szFormatString, my_args);
va_end(my_args);
}
static void AppendToLog(const char *szFormatString, va_list argptr)
{
char szLine[MAX_LENGTH_STRING] = {0};
if ((NULL != szFormatString) && (0 != strcmp(szFormatString, ""))) {
if (strlen(szFormatString) > MAX_LENGTH_STRING) {
return;
}
#ifdef WIN32
_vsnprintf(szLine, MAX_LENGTH_STRING-1, szFormatString, argptr);
#endif
...
}
and the VC show that it was broken at:
_VALIDATE_RETURN( (ch != _T('\0')), EINVAL, -1); (output.c)
I don't know why.
According to MSND, it should return a value whether it was ok or not.
This is canonical code for using vsnprintf:
void Format( const char * fmt, ... ) {
const int BUFSIZE = 1024;
char buffer[BUFSIZE];
va_list valist;
va_start( valist, fmt );
vsnprintf( &buf[0], BUFSIZE, fmt, valist );
va_end( valist );
// do something with buffer
}
I don't know if this helps, but keep in mind that vsnprintf (and _vsnprintf I guess since Microsoft says they're identical) return different values on Windows and Unix. The Windows version returns -1 if you overflow the buffer, while the Unix version returns how many characters would have been written had the buffer been large enough. Here's a couple of links that I found helpful in this regard:
http://msdn.microsoft.com/en-us/library/1kt27hek(v=vs.80).aspx
http://bytes.com/topic/c/answers/590845-snprintf-return-value
EDIT: And here's an alternate version I found to get around this problem:
http://article.gmane.org/gmane.comp.version-control.git/75280/