How to detect if building with address sanitizer when building with gcc 4.8?
From the GCC 4.8.0 manual: __SANITIZE_ADDRESS__ This macro is defined, with value 1, when -fsanitize=address is in use.
gcc
Declaring the array size with a non-constant variable
This is a GCC extension to the standard: You can use the -pedantic option to cause GCC to issue a warning, or -std=c++98 to make in an error, when you use one of these extensions (in case portability is a concern).
Bitshift and integer promotion?
The so-called usual arithmetic conversions apply to many binary operators, but not all of them. For example they do not apply to the bit shift operators, &&, ||, comma operator, and assignment operators. This is the rule for the bit shift operators: 6.5.7 … 3 Semantics … The integer promotions are performed on each of … Read more
How do I run the preprocessor on local headers only?
How much effort are you willing to go to? There’s an obnoxiously obscure way to do it but it requires you to set up a dummy directory to hold surrogates for the system headers. OTOH, it doesn’t require any changes in any of your source code. The same technique works equally well for C code. … Read more
GCC options for strictest C code? [duplicate]
I’d recommend using: -Wall -Wextra -std=c89 -pedantic -Wmissing-prototypes -Wstrict-prototypes \ -Wold-style-definition You should compile with -O as well as -g as some warnings are only available when the optimizer is used (actually, I usually use -O3 for spotting the problems). You might prefer -std=gnu89 as that disables fewer extensions in the libraries. OTOH, if you’re … Read more
Why does gcc -Wall give warning about zero-length format string?
The fact that GCC issues a warning usually has nothing to do with whether the construct is legal C, but whether the GCC developers consider it either a likely indication that you meant something other than what you write, or just bad style. Here are some examples: if (x = 0) — you almost surely … Read more
What is “strip” (GCC application) used for?
From the (Mac OS X, but others are similar) man page: strip removes or modifies the symbol table attached to the output of the assembler and link editor. This is useful to save space after a program has been debugged and to limit dynamically bound symbols. Note the bit about “after a program has been … Read more
If a global variable is initialized to 0, will it go to BSS?
Compiler is free to put such variable into bss as well as into data. For example, GCC has a special option controlling such behavior: -fno-zero-initialized-in-bss If the target supports a BSS section, GCC by default puts variables that are initialized to zero into BSS. This can save space in the resulting code. This option turns … Read more
Assigning 128-bit integer in C
Am I doing something wrong or is this a bug in gcc? The problem is in 47942806932686753431 part, not in __uint128_t p. According to gcc docs there’s no way to declare 128 bit constant: There is no support in GCC for expressing an integer constant of type __int128 for targets with long long integer less … Read more
what is meanging of gcc option “-fmessage-length”?
I didnt find it in GCC Command-Line Options. That’s because you’re looking at “a modified version of the Command-Line Options section of the GCC Manual.” This is the official list of all possible GCC command-line options, which leads to this section: “3.7 Options to Control Diagnostic Messages Formatting”. This is what the section has to … Read more