Recent questions tagged C

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What is the defined behavior in C for UINT_MAX + 1u? How safe is to assume it is zero? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Passing va_list to other functions

I have been trying to pass variable arguments to other function in C but it is producing inconsistent result in ... the reason for "438656664". See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Bitwise transpose of 8 bytes

I am looking for an efficient algorithm in C to bitwise-transpose 8 bytes of data. What I mean with this ... ) All ideas are much appreciated! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Adding Linker Flags in Xcode

(I'm not sure if "flag" is the word I'm looking for, but I'll explain it.) I am trying to compile a ... I add the lgmp flag while using Xcode? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - getpid and getppid return two different values

When I run the code below #include <stdio.h> #include <sys/types.h> //int i=0; int main(){ int id ; id = ... (1)? Shouldn't those two be equal? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - atomic create file if not exists from bash script

In system call open(), if I open with O_CREAT | O_EXCL, the system call ensures that the file will only be ... Just use mkdir. Mkdir is atomic See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How to determine ARMv8 features at runtime on iOS?

I am trying to determine when optional ARMv8 cpu features are available on iOS at runtime. On OS X ... #endif /* !_SYS_IOCTL_COMPAT_H_ */ See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Why can't gcc find the random() interface when -std=c99 is set?

I do "#include <stdlib.h>" at the top of the source. Example compilation: /usr/bin/colorgcc -std=c99 -fgnu89- ... there some trick I'm missing? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Can a "container_of" macro ever be strictly-conforming?

A commonly-used macro in the linux kernel (and other places) is container_of, which is (basically) defined as ... my answer to this question. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Preprocessor equality test, is this standard?

I had envisaged one of these in the project preferences TESTING = HOST TESTING = TARGET TESTING not defined ... standard acually requires this. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Finding stack frame size

The stack frame of a caller function can be easily obtained via __builtin_frame_address(1), but what about the ... of the caller function? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - What to do if a posix close call fails?

On my system (Ubuntu Linux, glibc), man page of a close call specifies several error return values it can ... file descriptors or whatever else? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Equivalence of p[0] and *p for incomplete array types

Consider the following code (it came about as a result of this discussion): #include <stdio.h> void foo(int (*p)[]) { ... )[]' and 'int (*)[3]' See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - initialization of anonymous structures or unions in C1X

I have the following question: How are anonymous structures (or unions) properly initialized according to the ... violation of the standard? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Reading Zend Engine API code: What does ## (double hash) mean?

Out of curiousity, I'm reading the Zend Engine API code and encountered quite a number of ## in their #define' ... mean in these two lines? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Do I really need libgcc?

I've been using GCC 4.6.2 on Mac OS X 10.6. I use the -static-libgcc option when I compile, ... Any insight into this would be appreciated! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - (.text+0x20): undefined reference to `main' and undefined reference to function

I am having issue getting my makefile to work without errors. The first issue i have is with an undefined reference to ... clean: rm -f *.o See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Cast void pointer to integer array

I have a problem where I have a pointer to an area in memory. I would like to use this pointer to create ... it. Any help would be appreciated. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Totally fed-up with get Gtk widget height and width

Trying to get Height and Width of GtkEventBox. Tried following Things. GtkRequisition requisition; ... of GtkWidget? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How does modulus of a smaller dividend and larger divisor work?

7 % 3 = 1 (remainder 1) how does 3 % 7 (remainder ?) work? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Calculate the size to a Base 64 encoded message

I have a binary string that I am encoding in Base 64. Now, I need to know before hand the size of the final Base ... , the code is in C. Thanks. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Is there a way to both check a macro is defined and it equals a certain value at the same time

I regularly use object-like preprocessor macros as boolean flags in C code to turn on and off sections of code ... used inside a #if statement. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Is a malloc() needed before a realloc()?

Since I had read realloc will act as malloc if the size pointed is 0, I was using it without malloc(), provided ... to malloc(1). Is it needed? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - 1 = false and 0 = true?

I came across an is_equals() function in a c API at work that returned 1 for non-equal sql tables (false) and ... of the API making an error? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Why did POSIX mandate CHAR_BIT==8?

There's a note in the POSIX rationale that mandating CHAR_BIT be 8 was a concession made that was necessary ... POSIX made no such requirement. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - "Multiple definition", "first defined here" errors

I have 3 projects: Server, Client and Commons. Making header & source pairs in Commons doesn't cause ... Neither does restarting the computer. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Why does const int main = 195 result in a working program but without the const it ends in a segmentation fault?

Consider following C program (see live demo here). const int main = 195; I know that in the real world no ... in the behavior of the program? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Should we break the default case in switch statement?

Assuming this example code (source): #include <stdio.h> void playgame() { printf( "Play game called" ); } void ... . Why? Is there a reason? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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