https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109368
Bug ID: 109368
Summary: LTO drops entry point symbol
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: pali at kernel dot org
CC: marxin at gcc dot gnu.org
Target Milestone: ---
Target: Mingw32
LTO for PE executables drops entry point symbol when the default entry point is
used. There is no warning and just PE AddressOfEntryPoint is zeroed. Which
results in broken PE binary.
When non-default entry point is used and specified via -e option then LTO does
not drop entry point symbol and generates working PE executable.
Simple test case which does not use any system library or startup file:
$ cat test-nostartfiles.c
int mainCRTStartup(void) { return 0; }
Default console binary has entry point mainCRTStartup() function (as hardcoded
in LD sources).
$ i686-w64-mingw32-gcc -Wall -Wextra -nostartfiles -nodefaultlibs -nostdlib
test-nostartfiles.c -o test-nostartfiles.exe
Without LTO it generates working PE binary which correctly returns 0 to system.
It also has correct AddressOfEntryPoint field in PE:
$ i686-w64-mingw32-objdump -p test-nostartfiles.exe | grep AddressOfEntryPoint
AddressOfEntryPoint 00001000
When compiling with LTO it does not throw any warning but generates broken PE
binary:
$ i686-w64-mingw32-gcc -Wall -Wextra -nostartfiles -nodefaultlibs -nostdlib
test-nostartfiles.c -o test-nostartfiles.exe -flto
Trying to run it, it crashes and has zeroed AddressOfEntryPoint:
$ i686-w64-mingw32-objdump -p test-nostartfiles.exe | grep AddressOfEntryPoint
AddressOfEntryPoint 00000000
When non-default entry point is used (specified via -e option) then LTO works
correctly and does not drop its entry point.
$ cat test-nostartfiles2.c
int my_entry(void) { return 0; }
$ i686-w64-mingw32-gcc -Wall -Wextra -nostartfiles -nodefaultlibs -nostdlib -e
_my_entry test-nostartfiles2.c -o test-nostartfiles2.exe -flto
$ i686-w64-mingw32-objdump -p test-nostartfiles2.exe | grep AddressOfEntryPoint
AddressOfEntryPoint 00001000
Compiled binary works fine.
So there is a bug in LTO compiler that it drops entry point if default one is
used (i.e. when entry point is not specified via -e option).
