Hi! This again, I think I cracked it into sensible chunks (see below) and addressed most-all reviews (reviewers CC:d). I also reduced the overly-verbose flag list (which was already missing -std=c18) to "standards conformance (-ansi, -std=c*)", added a VLA paragraph, and elucidated on the commit messages (#1 even has references and everything). наб (5): strdup.3: drop mention of "the GNU GCC suite" alloca.3: clarify origins in CONFORMING TO alloca.3: clarify reasoning for no error return in BUGS alloca.3: remove GCC faffling from NOTES alloca.3: simplfy malloc(3) suite comparison, note VLAs man3/alloca.3 | 76 +++++++++++++++++++-------------------------------- man3/strdup.3 | 3 -- 2 files changed, 28 insertions(+), 51 deletions(-) Interdiff against v1: diff --git a/man3/alloca.3 b/man3/alloca.3 index 133ca6ab3..736182a7d 100644 --- a/man3/alloca.3 +++ b/man3/alloca.3 @@ -90,7 +90,7 @@ originates from PWB and 32V, and appears in all their derivatives. The .BR alloca () function is machine- and compiler-dependent. -Because it allocates from the stack, it's always faster than +Because it allocates from the stack, it's faster than .BR malloc (3)/ free (3). In certain cases, it can also simplify memory deallocation in applications that use @@ -124,28 +124,32 @@ By necessity, .BR alloca () is a compiler built-in, also known as .BR __builtin_alloca (). -By default, modern compilers automatically translate plain +By default, modern compilers automatically translate all uses of .BR alloca () -calls, but this is forbidden if -.IR "\-ansi" , -.IR "\-std=c89" , -.IR "\-std=c99" , -or -.IR "\-std=c11" -are specified, in which case +into the built-in, but this is forbidden if standards conformance is requested +.RI ( "\-ansi" , +.IR "\-std=c*" ), +in which case .I <alloca.h> -is required, lest an actual symbol dependency is emitted. +is required, lest a symbol dependency be emitted. .PP The fact that .BR alloca () is a built-in means it is impossible to take its address or to change its behavior by linking with a different library. +.PP +Variable length arrays (VLAs) are part of the C99 standard, +optional since C11, and can be used for a similar purpose. +However, they do not port to standard C++, and, being variables, +live in their block scope and don't have an allocator-like interface, +making them unfit for implementing functionality like +.BR strdupa (3). .SH BUGS -As it's untestable, there is no error indication if the allocation -would overflow the space available for the stack. +Due to the nature of the stack, it is impossible to check if the allocation +would overflow the space available, and, hence, neither is indicating an error. (However, the program is likely to receive a .B SIGSEGV -signal if it attempts to access that space.) +signal if it attempts to access unavailable space.) .PP On many systems .BR alloca () -- 2.20.1
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