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Questions tagged [gcc-warning]

GCC is the GNU Compiler Collection, encompassing the gcc C compiler and the g++ C++ compiler, among others. It has powerful warning facilities that can reveal coding errors in C and C++ code.

GCC is the GNU Compiler Collection, a collection of language compilers that use the same underlying infrastructure. The most prominent are gcc, for C, and g++, for C++. All GCC compilers have similar warning facilities, starting with -Wall and including many other -W flags. These warnings can be extremely helpful in diagnosing problems with code and improving coding style and portability.

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WARNING: "implicit declaration of function '...' is invalid in C99"

I'm getting this warning when I'm trying to compare RGB components of two UIColors In .h file, I declared this -(int) ColorDiff:(UIColor *) color1 :(UIColor *)color2; In .m file - (int) ColorDiff:(UIColor *) color1 :(UIColor *)color2{ ...…
JHHoang
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Tell gcc that a function call will not return

I am using C99 under GCC. I have a function declared static inline in a header that I cannot modify. The function never returns but is not marked __attribute__((noreturn)). How can I call the function in a way that tells the compiler it will not…
Tom
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Don't understand "assuming signed overflow" warning

I am getting: warning: assuming signed overflow does not occur when assuming that (X + c) < X is always false [-Wstrict-overflow] on this line: if ( this->m_PositionIndex[in] < this->m_EndIndex[in] ) m_PositionIndex and m_EndIndex of type…
David Doria
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Is there any way to get readable gcc error and warning output at the command line?

For some long errors, the gcc output is dense and has lots of line-wrapping etc. Especially when errors are subtle, it can take me 10-30 seconds of squinting to parse it with my eyes. I've taken to pasting this in an open code-editor window to get…
mikeh
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Disable warnings being treated as errors (cc1.exe)

I am developing a BREW application. When compiling the application to get a MOD file, I am continuously getting this error: cc1.exe: warnings being treated as errors I want to disable this warning. I have googled it, and many say disabling -werror…
Sarim Sidd
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How to make gcc warn about passing wrong enum to a function

gcc doesn't seem to produce a warning with the following code. How can I get it to produce a warning? typedef enum { REG8_A, REG8_B, REG8_C }REG8; typedef enum { REG16_A, REG16_B, REG16_C }REG16; void function(REG8…
Rocketmagnet
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Suppress Compiler warning Function declared never referenced

So i have some code like this: void foo (int, int); void bar ( ) { //Do Stuff #if (IMPORTANT == 1) foo (1, 2); #endif } When doing a compile without "IMPORTANT" I get a compiler Warning that foo is defined and never referenced.…
Jtello
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Meaning of the g++ flags "-Wall", " -W", and "-Werror"

What are these and what do they do? -Wall -W -Werror I am using the terminal in Ubuntu to compile programs with this command: g++ -Wall -W -Werror main.cpp -o exec What is the explanation?
Mudit Kapoor
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Why does GCC not warn for unreachable code?

Why doesn't GCC (4.6.3) give me any warning for the unreachable code in the below example? #include int status(void) { static int first_time = 1; if (first_time) { return 1; first_time = 0; /* Never reached */ …
Andreas Haas
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How to make gcc warn undefined struct?

I have a struct defined in .h struct buf_stats { // *** }; then in .c file struct buf_stats *bs = malloc(sizeof(struct buf_states*)) ; where buf_states is a typo. but gcc does not warn me, although I used -Wall and this bug/typo cost me 3 hours…
Sato
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How to print the address of a function?

I let gcc compile the following example using -Wall -pedantic: #include int main(void) { printf("main: %p\n", main); /* line 5 */ printf("main: %p\n", (void*) main); /* line 6 */ return 0; } I get: main.c:5: warning: format ‘%p’…
alk
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Error: this statement may fall through [-Werror=implicit-fallthrough=]

I am trying to compile mitk on ubuntu and I got this error : error: this statement may fall through [-Werror=implicit-fallthrough=] Here there is a part of code : /** Get memory offset for a given image index */ unsigned int…
agasim
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Have compiler check the number of array initializers

Initializing an array (in C++, but any solution which works for C will likely work here as well) with less initializers than it has elements is perfectly legal: int array[10] = { 1, 2, 3 }; However, this can be a source of obscure bugs. Is there a…
MvG
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GCC v12.1 warning about serial compilation

I have upgraded my whole arch linux system today (12th May, 2022). gcc was also upgraded from v11.2 to v12.1. I tried compiling some of my programs with g++ (part of gcc compiler collection) by the following command: g++ -O3 -DNDEBUG -Os -Ofast -Og…
Darth-CodeX
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Why doesn't GCC produce a warning when assigning a signed literal to an unsigned type?

Several questions on this website reveal pitfalls when mixing signed and unsigned types and most compilers seem to do a good job about generating warnings of this type. However, GCC doesn't seem to care when assigning a signed constant to an…
maerics
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