Tag: c,io,fortran,shared-libraries,abi
If I have a Fortran subroutine which takes a Fortran IO Unit as one of its parameters (for printing debug information to), and this function is compiled into a shared library, how do I correctly call this function from C?
! An example subroutine that I want to call from C:
subroutine hi(unit)
integer :: unit
write(unit,*) "hello"
end subroutine
! example call site in Fortran
program main
call hi(6)
end
I am interested in how these unit numbers relate to file descriptors.
This is completely compiler dependent, there is no portable correspondence. See the manual of your compiler if they support some sort of interoperability as an extension.
What strlen does is basically count all bytes until it hits a zero-byte, the so-called null-terminator, character '\0'. So as long as the string contains a terminator within the bounds of the memory allocated for the string, strlen will correctly return the number of char in the string. Note that...
c,linux,memory,stack,portability
Q 1. why is ch empty even after fread() assignment? (Most probably) because fread() failed. See the detailed answer below. Q 2.Is this a portability issue between Solaris and Linux? No, there is a possible issue with your code itself, which is correctly reported by valgrind. I cannot quite...
As mentioned in the cgo documentation: As Go doesn't have support for C's union type in the general case, C's union types are represented as a Go byte array with the same length. Another SO question: Golang CGo: converting union field to Go type or a go-nuts mailing list post...
c,arrays,segmentation-fault,initialization,int
In your code, int i is an automatic local variable. If not initialized explicitly, the value held by that variable in indeterministic. So, without explicit initialization, using (reading the value of ) i in any form, like array[i] invokes undefined behaviour, the side-effect being a segmentation fault. Isn't it automatically...
c,increment,undefined-behavior
There is no undefined behavior in this code. i=i+1; is well-defined behavior, not to be confused with i=i++; which gives undefined behavior. The only thing that could cause different outputs here would be floating point inaccuracy. Try value += 4 * (int)nearbyint(pow(10,i)); and see if it makes any difference....
If you need bit k (k = 0 ..15), you can do the following: return (lfsr >> k) & 1; This shifts the register kbit positions to the right and masks the least significant bit....
c,visual-studio-2012,linker,static-libraries
C++ uses something called name mangling when it creates symbol names. It's needed because the symbol names must contain the complete function signature. When you use extern "C" the names will not be mangled, and can be used from other programming languages, like C. You clearly make the shunt library...
Yes, this is correct. The only danger would be generating a bit pattern that does not correspond to any int, but on modern systems there are no such patterns. Also, if the data type was uint32_t specifically, those are prohibited from having any such patterns anyway. Note that the inverse...
c,integer,compare,bit-manipulation,string-comparison
It's possible to do this using bit-manipulation. Space your values out so that each takes up 5 bits, with 4 bits for the value and an empty 0 in the most significant position as a kind of spacing bit. Placing a spacing bit between each value stops borrows/carries from propagating...
The pointer + offset notation is used as a convenient means to reference memory locations. In your case, the pointer is provided by malloc() after allocating sufficient heap memory, and represents an array of M + 2 elements of type char, thus the notation as used in your code represents...
In your first code, Case 1: return reverse(i++); will cause stack overflow as the value of unchanged i will be used as the function argument (as the effect of post increment will be sequenced after the function call), and then i will be increased. So, it is basically calling the...
My C is a bit rusty but your code made many rookie mistakes. execl will replace the current process if it succeeds. So the last line ("i have no idea why") won't print if the child can launch successfully. Which means... execl failed and you didn't check for it! Hint:...
Which man page are you quoting? There are multiple man pages available, not all mapping to the same OpenGL version. Anyways, the idea behind the + 2 (border) is to have 2 multiplied by the value of border, which is in your case 0. So your code is just fine....
c,arrays,pebble-watch,cloudpebble
The problem is this line static char *die_label = "D"; That points die_label to a region of memory that a) should not be written to, and b) only has space for two characters, the D and the \0 terminator. So the strcat is writing into memory that it shouldn't be....
"local" in this context means file scope. That is: static int local_data = 1; /* initialised local data */ static int local_bss; /* uninitialised local bss */ int global_data = 1; /* initialised global data */ int global_bss; /* uninitialised global bss */ void main (void) { // Some code...
c,arrays,compilation,compiler-errors,include
include is a preprocessor directive that includes the contents of the file named at compile time. The code that conditionally includes stuff is executed at run time...not compile time. So both files are being compiled in. ( You're also including each file twice, once in the main function and once...
You can make the result of the input be const like this: int func() { int op = 0; scanf( "%d", &op ); if( op == 0 ) return 1; else return 2; } int main() { const int v = func(); // ... } NB. Of course, there is...
Mentioned solution with fseek is good. However, it can be very slow for large matrices (as disks don't like random access, especially very far away). To speed up things, you should use blocking. I'll show a basic concept, and can explain it further if you need. First, you split your...
c,char,segmentation-fault,user-input,scanf
I'm not saying that it cannot be done using scanf(), but IMHO, that's not the best way to do it. Instead, use fgets() to read the whole like, use strtok() to tokenize the input and then, based on the first token value, iterate over the input string as required. A...
Are DETUNE1 and DETUNE2 calculated every time it is called? Very unlikely. Because you are calling sqrt with constants, most compilers would optimize the call to the sqrt functions and replace it with a constant value. GCC does that at -O1. So does clang. (See live). In the general...
From printf's manual: The field width An optional decimal digit string (with nonzero first digit) specifying a minimum field width. If the converted value has fewer characters than the field width, it will be padded with spaces on the left (or right, if the left-adjustment flag has been given). Instead...
c,while-loop,char,scanf,getchar
That's because scanf() left the trailing newline in input. I suggest replacing this: ch = getchar(); With: scanf(" %c", &ch); Note the leading space in the format string. It is needed to force scanf() to ignore every whitespace character until a non-whitespace is read. This is generally more robust than...
What is happening is that tPeca pecaJogo[tam]; is a local variable, and as such the whole array is allocated in the stack frame of the function, which means that it will be deallocated along with the stack frame where the function it self is loaded. The reason it's working is...
Historically, lots of details about how signals work have changed. For instance, in the earliest variant, the processing of the signal reverted to default when the handler was called, and the handler had to re-establish itself. In this situation, sending the signal from the handler would kill the process. Currently,...
pub_l = malloc(sizeof(pub_l)); is simply not needed. Nor is priv_l = malloc(sizeof(priv_l));. Remove them both from your function. You should be populating your out-parameters; instead you're throwing out the caller's provided addresses to populate and (a) populating your own, then (b) leaking the memory you just allocated. The result is...
c,algorithm,security,math,encryption
This is not a power operator. It is the XOR operator. The thing that you notice for the XOR operator is that x ^ k ^ k == x. That means that your encryption function is already the decryption function when called with the same key and the ciphertext instead...
c,memory-management,out-of-memory,realloc
When you allocate/deallocate memory many times, it may create fragmentation in the memory and you may not get big contiguous chunk of the memory. When you do a realloc, some extra memory may be needed for a short period of time to move the data. If your algorithm does...
As I said in the comment section, this can be achieved using MultiWriter package main import ( "io" "log" "os" "os/exec" ) func main() { // Logging capability f, err := os.OpenFile("log.log", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666) if err != nil { log.Fatalf("Error opening file: %v", err) } defer f.Close() mwriter := io.MultiWriter(f,...
If you're "trying to allocate an array 64 bytes in size", you may consider uint8_t Buffer[64]; instead of uint8_t *Buffer[64]; (the latter is an array of 64 pointers to byte) After doing this, you will have no need in malloc as your structure with a 64 bytes array inside is...
Important: scanf(" %s", name); has no bounds checking on the input. If someone enters more than 255 characters into your program, it may give undefined behaviour. Now, you have the char array you have the count (number of char in the array), why do you need to bother doing stuffs...
Yes, you can do that. You need to use an asterisk * as the field width and .* as the precision. Then, you need to supply the arguments carrying the values. Something like sprintf(myNumber,"%*.*lf",A,B,a); Note: A and B need to be type int. From the C11 standard, chapter ยง7.21.6.1, fprintf()...
Yes, temp_uart_count will contain the actual number of bytes read, and obviously that number will be smaller or equal to the number of elements of temp_uart_data. If you get 0, it means that the end of file (or an equivalent condition) has been reached and there is nothing else to...
c,binary-tree,binary-search-tree
a sample to modify like as void inorder ( struct btreenode *, int ** ) ; int* sort(int *array, int arr_size) { struct btreenode *bt = NULL; int i, *p = array; for ( i = 0 ; i < arr_size ; i++ ) insert ( &bt, array[i] ) ;...
#include <stdio.h> int main() { unsigned int i = 0x557e89f3; unsigned char c[4]; c[0] = i & 0xFF; c[1] = (i>>8) & 0xFF; c[2] = (i>>16) & 0xFF; c[3] = (i>>24) & 0xFF; printf("c[0] = %x \n", c[0]); printf("c[1] = %x \n", c[1]); printf("c[2] = %x \n", c[2]); printf("c[3] =...
Programs simply do not take integers as arguments, they take strings. Those strings can be decimal representations of integers, but they are still strings. So you are asking how to do something that simply doesn't make any sense. Twenty is an integer. It's the number of things you have if...
I am assuming your pointer refers to 20 bytes, for the 160 bit value. (An alternative may be text characters representing hex values for the same 160 bit meaning, but occupying more characters) You can declare a class for the data, and implement a method to increment the low order...
The only difference between the two is the scope of the else. Without the braces, it spans until the end of the full statement, which is the next ;, i.e the next line: else putchar(ch); /* end of else */ lastch = ch; /* outside of if-else */ With the...
You can redirect the JOIN operation to another macro, which then does the actual pasting, in order to enforce expansion of its arguments: #define VAL1CHK 20 #define NUM 1 #define JOIN1(A, B, C) A##B##C #define JOIN(A, B, C) JOIN1(A, B, C) int x = JOIN(VAL,NUM,CHK); This technique is often used...
This code is broken for two reasons: Accessing a variable twice between sequence points, for other purposes than to determine which value to store, is undefined behavior. There are no sequence points between the evaluation of function parameters. Meaning anything could happen, your program might crash & burn (or more...
c,percentage,integer-overflow,integer-division
Diagnosis The value you expect is, presumably, 91. The problem appears to be that your compiler is using 16-bit int values. You should identify the platform on which you're working and include information about unusual situations such as 16-bit int types. It is reasonable for us to assume 32-bit or...
If you are only looking for fields that match the input, you'll want to search the database using the input string. In other words, write your query string so that it only gives you results that match the user input. This will be much faster than searching through every returned...
Every time you are creating your string, you are not appending a null terminator, which causes the error. So change this: for(j=0; j<rem_len; j++) { if(j != i) { remaining_for_next[index_4_next] = remaining[j]; index_4_next++; } } to this: for(j=0; j<rem_len; j++) { if(j != i) { remaining_for_next[index_4_next] = remaining[j]; index_4_next++; }...
Well according to this page: http://www.keil.com/support/man/docs/armccref/armccref_BABJFEFG.htm You have __BIG_ENDIAN which is defined when compiling for a big endian target....
c,embedded,stm32,gnu-arm,coocox
I've found the reason: that's because stack size is actually fixed and it is located in heap (if I could call it heap). In file startup_stm32f10x*.c there is a section: /*----------Stack Configuration----------*/ #define STACK_SIZE 0x00000100 /*!< The Stack size suggest using even number */ And at then very next line:...
In binary any numbers LSB (Least Significant Bit) is set or 1 means the number is odd, and LSB 0 means the number is even. Lets take a look: Decimal binary 1 001 (odd) 2 010 (even) 3 011 (odd) 4 100 (even) 5 101 (odd) SO, the following line...
There are few fixes required in the code: CallIntMethod should be (*env)->CallIntMethod class Test should be public Invocation should be jint age = (*env)->CallIntMethod(env, mod_obj, mid, NULL); Note that you need class name to call a static function but an object to call a method. (cls2 -> person) mid =...
c,pointers,dynamic-memory-allocation,behavior,realloc
Yes, ptr2 is unaffected by realloc(), it has no connection to realloc() call whatsoever(as per the current code). However, FWIW, as per the man page of realloc(), (emphasis mine) The realloc() function returns a pointer to the newly allocated memory, which is suitably aligned for any kind of variable and...
The scanf family of functions are good for simple parsing, but not for more complicated things like you seem to do. You could probably solve it by using e.g. strstr to find the comment starter "//", terminate the string there, and then remove trailing space....
The string bound to "s" will be deallocated once the function ends ("s" goes out of scope), so you cannot return a reference to its contents outside the function. The best way is to return the string itself: fn read_shader_code(string_path: &str) -> String { let path = Path::new(string_path); let display...
c,mpi,intel-mkl,mpich,scalapack
This answer is courtesy of Ying from Intel, all the credits go to him! The int in C are supposed to be 32bit, you may try lp64 mode. mpicc -o test_lp64 ex1.c -I/opt/intel/mkl/include /opt/intel/mkl/lib/intel64/libmkl_scalapack_lp64.a -L/opt/intel/mkl/lib/intel64 -Wl,--start-group /opt/intel/mkl/lib/intel64/libmkl_intel_lp64.a /opt/intel/mkl/lib/intel64/libmkl_core.a /opt/intel/mkl/lib/intel64/libmkl_sequential.a -Wl,--end-group /opt/intel/mkl/lib/intel64/libmkl_blacs_intelmpi_lp64.a -lpthread -lm -ldl [[email protected] scalapack]$ mpirun -n 4...