Fix vfprintf and derived functions not handling write errors (#798)

The C standard states:
> The fprintf function returns the number of characters transmitted,
> or a negative value if an output or encoding error occurred or if
> the implementation does not support a specified width length
> modifier.
- C Standard, 7.23.6.1.15. The fprintf function

However, cosmopolitan fails to return a negative value in the case of
an output error, meaning that a program such as:

 #include <stdio.h>

int main()
{
    FILE *fp = fopen("/dev/full", "w");

    setbuf(fp, NULL);
    printf("fprintf: %d\n", fprintf(fp, "test\n"));
    printf("fflush: %d\n", fflush(fp));
}

will, under cosmopolitan, print that no error occured in either of the
calls to fprintf and fflush.

This patch fixes this, along with the associated GitHub issue,
https://github.com/jart/cosmopolitan/issues/784
This commit is contained in:
Gabriel Ravier 2023-03-31 15:57:29 +02:00 committed by GitHub
parent 221adfa606
commit 9c6d78c26d
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
3 changed files with 38 additions and 1 deletions

View file

@ -55,6 +55,9 @@ $(TEST_LIBC_FMT_OBJS): private \
DEFAULT_CCFLAGS += \
-fno-builtin
o/$(MODE)/test/libc/fmt/fprintf_test.com.runs: \
private .UNVEIL += w:/dev/full
.PHONY: o/$(MODE)/test/libc/fmt
o/$(MODE)/test/libc/fmt: \
$(TEST_LIBC_FMT_BINS) \