<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/72599>72599</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
[Flang] Unexpected behavior of file positioning statements and data transfer statements for unformatted records
</td>
</tr>
<tr>
<th>Labels</th>
<td>
flang:runtime
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
yus3710-fj
</td>
</tr>
</table>
<pre>
This is an issue from Fujitsu testsuite.
The execution of a program compiled by flang-new terminates with a fatal error.
In the program, there is a `BACKSPACE` statement after some output statements for unformatted records. Then, a record is read and another output statement is executed.
The following are the test program, Flang-new and gfortran execution result.
```fortran
! test.f90
integer dim1(704),dim2(704)
do i=1,704
dim1(i) = i
end do
rewind 4
write (4) (dim1(i),i=1,704)
write (4) (dim1(i),i=1,302)
write (4) (dim1(i),i=1,704)
backspace 4
read (4) (dim2(i),i=1,704)
write (4) (dim1(i),i=1,302)
write (4) (dim1(i),i=1,201)
rewind 4
read (4) (dim2(i),i=1,704)
read (4) (dim2(i),i=1,302)
read (4) (dim2(i),i=1,704)
read (4) (dim2(i),i=1,302)
read (4) (dim2(i),i=1,201)
print *, "ok"
end
```
```console
$ flang-new -v test.f90
flang-new version 18.0.0 (https://github.com/llvm/llvm-project.git acef83c142619abf270145c91093c76c9d6d5ede)
Target: aarch64-unknown-linux-gnu
Thread model: posix
InstalledDir: /path/to/install/bin
Found candidate GCC installation: /opt/rh/gcc-toolset-12/root/usr/lib/gcc/aarch64-redhat-linux/12
Selected GCC installation: /opt/rh/gcc-toolset-12/root/usr/lib/gcc/aarch64-redhat-linux/12
Candidate multilib: .;@m64
Selected multilib: .;@m64
"/path/to/install/bin/flang-new" -fc1 -triple aarch64-unknown-linux-gnu -emit-obj -fcolor-diagnostics -mrelocation-model pic -pic-level 2 -pic-is-pie -target-cpu generic -target-feature +neon -target-feature +v8a -o /tmp/test-94bdd9.o -x f95-cpp-input test.f90
"/opt/rh/gcc-toolset-12/root/usr/lib/gcc/aarch64-redhat-linux/12/../../../../bin/ld" -pie -EL --hash-style=gnu --eh-frame-hdr -m aarch64linux -dynamic-linker /lib/ld-linux-aarch64.so.1 -o a.out /lib/../lib64/Scrt1.o /lib/../lib64/crti.o /opt/rh/gcc-toolset-12/root/usr/lib/gcc/aarch64-redhat-linux/12/crtbeginS.o -L/path/to/install/lib/clang/18/lib/aarch64-unknown-linux-gnu -L/opt/rh/gcc-toolset-12/root/usr/lib/gcc/aarch64-redhat-linux/12 -L/opt/rh/gcc-toolset-12/root/usr/lib/gcc/aarch64-redhat-linux/12/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/lib -L/usr/lib /tmp/test-94bdd9.o -L/path/to/install/lib -lFortran_main -lFortranRuntime -lFortranDecimal -lm -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /opt/rh/gcc-toolset-12/root/usr/lib/gcc/aarch64-redhat-linux/12/crtendS.o /lib/../lib64/crtn.o
$ ./a.out
fatal Fortran runtime error(/path/to/test.f90:20): Unformatted variable-length sequential file input failed at record #3 (file offset 4036): record header has length 2816 that does not match record footer (1208)
Aborted (core dumped)
```
```console
$ gfortran -v test.f90
Driving: gfortran -v test.f90 -l gfortran -l m -shared-libgcc
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/aarch64-redhat-linux/8/lto-wrapper
Target: aarch64-redhat-linux
Configured with: ../configure --enable-bootstrap --enable-languages=c,c++,fortran,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=https://bugs.rockylinux.org/ --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl --disable-libmpx --enable-gnu-indirect-function --build=aarch64-redhat-linux
Thread model: posix
gcc version 8.5.0 20210514 (Red Hat 8.5.0-18) (GCC)
:
$ ./a.out
ok
```
It seems that information of the length of a record gets wrong.
```fortran
! test2.f90
integer dim1(704),dim2(704)
do i=1,704
dim1(i) = i
end do
rewind 4
write (4) (dim1(i),i=1,704)
write (4) (dim1(i),i=1,302)
write (4) (dim1(i),i=1,704)
!backspace 4
!read (4) (dim2(i),i=1,704)
write (4) (dim1(i),i=1,302)
write (4) (dim1(i),i=1,201)
rewind 4
read (4) (dim2(i),i=1,704)
read (4) (dim2(i),i=1,302)
read (4) (dim2(i),i=1,704)
read (4) (dim2(i),i=1,302)
read (4) (dim2(i),i=1,201)
print *, "ok"
end
```
```console
$ flang-new test.f90 && ./a.out
fatal Fortran runtime error(/path/to/test.f90:20): Unformatted variable-length sequential file input failed at record #3 (file offset 4036): record header has length 2816 that does not match record footer (1208)
Aborted (core dumped)
$ od -i fort.4 > ng
$ flang-new test2.f90 && ./a.out
ok
$ od -i fort.4 > ok
$ diff ok ng
429c429
< 0015300 702 703 704 2816
---
> 0015300 702 703 704 1208
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzsWd1v47gR_2uYlwENifLnQx68dnwtGuAOuzn0MaDJkcQNRepIKh_96wtSki1nk9wucNcW6C28jsXhfP04nBlS3HtVGcRrsvhEFvsr3oXauuuXzherPKPl16ujlS_Xd7XyoDxwA8r7DqF0toFD91UF30FAH3ynAs5ItifZtv--qxHwGUUXlDVgS-DQOls53oCwTas0Sji-QKm5qajBJwjoGmV4QA9PKtTAoeSBa0DnrLsQ_XcDocZRHGG7-OgwWQhkmX3a7v7x5Zft7oYsM_CBB2zQBOBlQAfeNgi2C20XzjQPpXXQmdK6hoeAEhwK66SfwV2NJqrgw1DU4pBL4Cb-t1H1N_LipN55lN-gUlqt7ZMyFXCHyZOI4NSdwwmUqKQqrQuOmwmcDn2nw4Vkssz6zzB7GGV5kj4rN1k_okzACh1I1eSErVfZnLANYTupGnZ-ngiWFhQp9jlhu0hMYzCyK8I2QIo9qJ6ARoK0U3aHT8pIGBifnAoIhK3niZGtJ3II200VjVZ8J0uRsR9lmWo5cvHgWy5wtDSt8aUI9t8ylGX5q0W5RPXHbf0-jqmp_zs6pmi0TpkAhG3jtiGM2QfC2BQoNPLV_nj1KKzxVuO4XeaTjEQfT3sHevqZ9ojOx52Yr2fZLIvG1iG0nhRbwg6EHSoV6u44E7Yh7KD14_iHts5-RRFmlQrABZbrQuRztsw3_FiyVZbPF2KTZ5tCrJZiI5dygRJP7t5xV2EgxRY4d6JezmlnHox9MlQr0z3TynRjnklYNlaijtNb69XzmD194Fqj3CsXSYQdWh5qwg7BEnZQPZmww1ENSeRgOyNBcCOV5AHhp90Ohmk8pqNBim0DYQcXJVVC0GCt9hhozuKotZHYeRdxUMd-DmGH0Q-Hsuahd4OwQz4s4hfUKGI-_g_q3J0cbTodVOQstjAjxScyz5rl_JVlH02KIfkhvuxwCinCGNBS5ECDU63G95cYKDYqUHv8Ghmsto5KxStjfVDCA20caisSTDRFALRKAG2VoBofUQPrH5SnrUKgIUUVFW0HFRp0cfIwViIPnYsp6pNBa94af1xzoDYuRmja-I0-0M38KOVmZoE-Q7lZUNG2VJlYIy-r0QDQH7yM7DCbffvV461lAjo5fnMLlNbc19SHF42k2Cd0Kda0dLxBWksHtBlXImkAKl8MbyKWyjygg5NVWg5LNEyfeTvLIzR8ZrtwnpeM0eq4nBN2-CJcyGf2HapwQfXEPxwh4cIRK2W-xEW6fTdIe3EiBmnkXJ-GPojO2z_c3j9D5jtRkqDv9b1ekH50quINjleT3t0XH0IOVB_6Nu6-4cqcHz93JqgGzwN7FKrhGqhugOpKCKCUe2oQJcp-5N4DpcZeDIvvn_wnBR8a-eWjuDcze67JkTbsoklt788HAxDgBmjSeYGw9St8T3mn2LIsFtRiC79OGv5H7hQ_aqQaTRVq8PhbhyYorqFUGqHPXiVPBxcextMAYUURq3-aY8vSY4B5ViwHDcOsGrlEBzX3MIhn63wJoeYBpEUPxgZoeBD1yFFaG1JyWecsW58agO3RupAWZS2sQ5Bd06I8N4ff2-SczhTf9jh7px6VqaL1b86iejKuoQHqa-4wJr9jXPkk5FcfzzfHTulAlQHfovDDcWX38-3tze7u_qfdLibci-PKSLu9-_n-n5-3v_xy85kU-2l4xTPQ74VYSlLB0ifH2xbde63TBVev3ppSVZ1DmY6gqaLH0BPjeKwNJkXJ0drgg-PteSjmyI5X6EmxF4TtBGGf0mc3-sh2OligtHVYqueTZ0BpE3sON_U1gUrYoYkwU2VK-86ESAJKo8H02FWd06TYXzajx67yM2fFw0tydmZdTOZny_sFPD-H1D1GP1LfeCaIGsVDCo69Q43cTxAZ-6DRFv_iAzb0X_3QMOn-Xjzzex7wWQWgVCrfQ6eOnYknGorPAtvYufgzU2U62hn1W4ex50ERJpinGkxjoEmq5Kg7ZqmGf7WODn06tUa_jNSB6a3C30ttdVfFrDs-K6NCqYyi3Dl-EqO8vnShaZ8vjVZxUVEEWnZGpIM77U0lxf79KPygd48pezx5rGeLWQYsY3m2yOcxI3xGCX_joafQWKvTKSputDFBQIyJd9Mq2Ie380h_cAjgERvfpy015M7hdifUOKa2dNczpLEKg4cnZ031A5cV7K_bit_RQlj-zYUFYflfdxb_93cW52LOloQtz1v8r8bpw8aJzcFKoApiRprNgRQ3YKr3EGYfQHxOom_JnBKlKkuwDyc9c7YR85NFxQ6yLF8UWQbjv1XGJr-Lye95wqXnpJSOIm5-SEQC7DLSruR1ITfFhl_hdb7Ksny9Wq02V_W1XCNb8eNysVwey0KUfCM3S9wscrnMFjzfXKlrlrEiz_NVxhhbbGa8nEuxWQqBuWQrIck8w4YrPdP6sYktyVV6t3C9YovN5krzI2qf3kswlsAnxXaI1LhdFvsrd50u1GJzQ-aZVj74s6yggk6vNdJdOlns4VeDz21_ZXPEmj8q62KpSvEXS2ysZLFpnbwU4LE-8MAh7hNfovuONwZXndPXP3YXGJu46Lon7JC8_3cAAAD__081mko">