From 42706f47c918b035dee82f4bad15bf6499592d1c Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Fri, 15 May 2015 15:47:37 +0200 Subject: CODING_STYLE: document alloca() DONTS --- CODING_STYLE | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/CODING_STYLE b/CODING_STYLE index 70f45bebb..00986eb43 100644 --- a/CODING_STYLE +++ b/CODING_STYLE @@ -121,7 +121,8 @@ no speed benefit, and on calls like printf() "float"s get promoted to "double"s anyway, so there is no point. -- Do not invoke functions when you allocate variables on the stack. Wrong: +- Do not mix function invocations with variable definitions in one + line. Wrong: { int a = foobar(); @@ -259,3 +260,12 @@ which will always work regardless if p is initialized or not, and guarantees that p is NULL afterwards, all in just one line. + +- Use alloca(), but never forget that it is not OK to invoke alloca() + within a loop or within function call parameters. alloca() memory is + released at the end of a function, and not at the end of a {} + block. Thus, if you invoke it in a loop, you keep increasing the + stack pointer without ever releasing memory again. (VLAs have better + behaviour in this case, so consider using them as an alternative.) + Regarding not using alloca() within function parameters, see the + BUGS section of the alloca(3) man page. -- cgit v1.2.3-65-gdbad