Setting stack size with g++-9 has no effect

Question

I'm building a test program with g++ 9.3.0 on Ubuntu 18.04 x64 using this linker command:

/usr/bin/g++-9  -O3 -DNDEBUG  -Wl,-z,stack-size=268435456 CMakeFiles/af.dir/main.cpp.o  -o af

I'm testing increased stack requirements with this function:

float f() {
  float a[3'000'000];
  return a[42];
}

and results indicate a standard 8MB stack regardless of the stack-size linker option value. What is the way to increase the stack size?

EDIT

The test is as follows:

float a[3'000'000]; causes Segmentation fault (core dumped)
float a[2'000'000]; returns 0 as expected

also: "results indicate a standard 8MB stack regardless" how do you test this? — nivpeled, May 10 '20 at 09:27
@nivpeled the apostrophe in integer literals were introduced to improve readability. Why not? — 463035818_is_not_an_ai, May 10 '20 at 09:30
On which platform are you ? that option does not work everywhere — bruno, May 10 '20 at 09:31
@M.M It doesn't complain about it. I tried different stack size option syntax variants and I was getting linker errors, but not for this one. — Paul Jurczak, May 10 '20 at 09:38
@M.M No. I could find only a cryptic reference to options (https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html) `-Wl,option` without a list of specific options. The internet is full of suggestions, which I tried a bunch of. I have a sneaky suspicion that you know more about this subject... — Paul Jurczak, May 10 '20 at 09:46
I don't, but my conclusion on seeing the option have no effect would be that the linker doesn't support it (for your platform at the least) — M.M, May 10 '20 at 09:59
You can [set the stack size at runtime](https://stackoverflow.com/questions/2279052/increase-stack-size-in-linux-with-setrlimit) btw, perhaps before entering whatever function uses the large amount — M.M, May 10 '20 at 10:03
@M.M Thank you, that worked just fine. Still, I would prefer to have a linker option, if there is one. — Paul Jurczak, May 10 '20 at 10:20

score 2 · Answer 1 · answered May 12 '20 at 05:54

2

It seems that setting stack size with g++ 9.3.0 linker options on Ubuntu 18.04 x64 is not possible. As suggested in comments, I settled for a run-time option:

#include <sys/resource.h>
#include <fmt/format.h>

int main() {
  if (struct rlimit rl{1<<28, 1l<<33}; setrlimit(RLIMIT_STACK, &rl))
    fmt::print("Can not set stack size! (errno = {})\n", errno);
  else
    fmt::print("Stack size: {}MiB up to {}GiB\n", rl.rlim_cur/(1<<20), rl.rlim_max/(1<<30));
...

answered May 12 '20 at 05:54

Paul Jurczak

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Could you report a bug in Launchpad (or maybe Binutils Bugzilla)? – yugr May 17 '20 at 08:32
@yugr I will if you point me to the documentation, which claims that `stack-size` option is functional in my environment. I searched and couldn't find a clear statement to this effect. – Paul Jurczak May 17 '20 at 11:06
Even if it doesn't, `ld` should emit a warning. – yugr May 17 '20 at 11:16
@yugr Can you post a link to appropriate bug reporting page? I don't know where linkers are made. – Paul Jurczak May 17 '20 at 12:37
1

I suggest to first file a bug in Ubuntu's own tracker, Launchpad ([here](https://bugs.launchpad.net/ubuntu/+source/binutils) is the page for Binutils bugs). They'll redirect it to https://sourceware.org/bugzilla/ if needed. – yugr May 17 '20 at 12:40
@yugr Done: https://bugs.launchpad.net/ubuntu/+source/binutils/+bug/1879154 – Paul Jurczak May 17 '20 at 13:15

Setting stack size with g++-9 has no effect

1 Answers1