https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96304
Bug ID: 96304
Summary: Possible mis-compile of SQLite for ARM using gcc 8.3.0
and -O2
Product: gcc
Version: 8.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: drh at sqlite dot org
Target Milestone: ---
Gcc 8.3.0 appears to be miscompiling SQLite for ARM when using -O2. A correct
build occurs with any other optimization setting, on X86_64, and with versions
of gcc in the 4.x.x timeframe (the only other versions tested). The bug
originates from two Gentoo bug reports against SQLite that claim the problem
also appears on PPC and SPARC, but I do not have appropriate hardware at hand
to verify that.
Unfortunately, I do not have a concise test case for you. However, I can
demonstrate the problem using one large C source file and one data file, as
described here: https://sqlite.org/forum/forumpost/c3e9c0edfa
We can work around the problem in SQLite by marking one particular function
using __attribute__((noinline)). You can see our work-around here:
https://www.sqlite.org/src/info/40c44d38104dfcb6
The forum post in the first link describes how to recreate the problem. I will
repeat that text here for completeness:
1. Download https://sqlite.org/tmp/gcc-problem-20200723/sftest.c (7.8MB) and
https://sqlite.org/tmp/gcc-problem-20200723/data1.db (252KB).
2. Compile using: "$GCC -O2 sftest.c"
3. Run like this: "./a.out run data1.db"
The expected output is "d1.db: 339 cases, 0 crashes" but the program hits an
assert() when compiled for ARM using -O2 using more recent versions of gcc
(newer than the 4.9.2 version that is the default on my raspberry PI).
Additional analysis of the problem is in the forum post and the check-in linked
above.
