https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126125
Bug ID: 126125
Summary: frontend stack overflow on `pragma Warnings (On|Off,
"*");` in -gnatec= config pragma file
Product: gcc
Version: 14.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ada
Assignee: unassigned at gcc dot gnu.org
Reporter: veriepic at horsefucker dot org
CC: dkm at gcc dot gnu.org
Target Milestone: ---
Created attachment 64946
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64946&action=edit
this is the repro mentioned in the description.
GNAT 14.2.0 (gcc 14.2.0, FSF build, x86_64-w64-mingw32) crashes with a
"Storage_Error stack overflow or erroneous memory access" frontend bug
when a configuration pragma file passed via `-gnatec=` contains:
pragma Warnings (On, "*");
or
pragma Warnings (Off, "*");
The crash is unconditional and reproduces on a minimal empty unit. The
same pragma in non-config-pragma context (inside a regular .ads/.adb
unit) compiles cleanly. Variants without the wildcard string -
`pragma Warnings (On);` or `pragma Warnings (On, "redundant");` -
compile fine in the same configuration pragma file. The trigger is
specifically the combination of:
1. -gnatec= (configuration pragma file)
2. pragma Warnings with two arguments
3. the second argument being the literal string "*"
On Windows the crash manifests as a Guard Page Exception (0x80000001)
when error reporting UI is enabled, indicating the recursion exhausts
the entire thread stack and tramples the OS guard page rather than
just the GNAT-internal stack overflow handler firing.
## reproducer
repro.adc:
pragma Warnings (On, "*");
empty.adb:
procedure Empty is
begin
null;
end Empty;
command:
gcc -c -gnatec=repro.adc empty.adb
## actual output
+===========================GNAT BUG
DETECTED==============================+
| 14.2.0 (x86_64-w64-mingw32) Storage_Error stack overflow or
|
| erroneous memory access
|
| Error detected at repro.adc:1:22
|
| Compiling empty.adb
|
+==========================================================================+
compilation abandoned
## expected output
Either successful compilation (if the wildcard form is intended to be
legal as a configuration pragma) or a clean diagnostic such as
`pragma Warnings ("*") is not allowed as a configuration pragma`
similar to other rejected config-pragma forms.
## bisect across pragma variants (all in -gnatec= config pragma file)
| pragma | result |
|---------------------------------------------------------|-----------------|
| pragma Warnings (On); | ok |
| pragma Warnings (Off); | ok |
| pragma Warnings (On, ""); | ok |
| pragma Warnings (On, "abc"); | ok |
| pragma Warnings (On, "redundant"); | ok (clean diag) |
| pragma Warnings (On, "?"); | ok |
| pragma Warnings (On, ".*"); | ok |
| pragma Warnings (On, "**"); | clean reject |
| pragma Warning_As_Error ("*"); | clean reject |
| pragma Warning_As_Error ("foo"); | ok |
| pragma Warnings (On, "*"); | STACK OVERFLOW |
| pragma Warnings (Off, "*"); | STACK OVERFLOW |
| pragma Warnings ("*"); | STACK OVERFLOW |
| pragma Warnings (On, "*", Reason => "x"); | STACK OVERFLOW |
| pragma Warnings (Off, "*", Reason => "x"); | STACK OVERFLOW |
Note that the related Warning_As_Error pragma cleanly rejects "*" while
the parallel Warnings pragma family enters unbounded recursion. This
suggests an issue in the wildcard-handling specific to Warnings pragma
processing inside config-pragma context.
environment:
gcc version 14.2.0 (GCC)
Target: x86_64-w64-mingw32
Configured with: ../src/configure
--prefix=/aaa/GNAT-FSF-builds/sbx/x86_64-windows64/gcc/install
--enable-languages=c,ada,c++ --enable-libstdcxx
--enable-libstdcxx-threads --enable-libada
--disable-nls --without-libiconv-prefix
--disable-libstdcxx-pch --enable-lto --disable-multilib
--enable-threads=win32 --with-gnu-ld --with-gnu-as
Thread model: win32
Distributed via Alire 2.0.2 (alire toolchain id 2540cccb).
Host OS: Windows 10
