diff options
| -rw-r--r-- | doc/HISTORY | 3 | ||||
| -rw-r--r-- | other/pamexec.c | 49 |
2 files changed, 49 insertions, 3 deletions
diff --git a/doc/HISTORY b/doc/HISTORY index f9daf84c..f1ed52ad 100644 --- a/doc/HISTORY +++ b/doc/HISTORY @@ -16,6 +16,9 @@ not yet BJH Release 10.94.00 are used except ppmtoilbm, so seeded results are the same on all platforms. + pamexec: Issue message instead of being killed by a signal when + the exec'ed program does not read the whole image" + pamscale: Fix bogus "bad magic number" or similar failure most of the time with -nomix. Broken since Netpbm 10.49 (December 2009). diff --git a/other/pamexec.c b/other/pamexec.c index 3d1f5086..cbde81ac 100644 --- a/other/pamexec.c +++ b/other/pamexec.c @@ -18,6 +18,8 @@ #include <stdbool.h> #include <string.h> #include <stdio.h> +#include <signal.h> +#include <setjmp.h> #include <errno.h> #include "pm_c_util.h" @@ -26,6 +28,26 @@ #include "mallocvar.h" #include "pam.h" + +/* About SIGPIPE: + + Unix has a strange function where by default, if you write into a pipe when + the reading side of the pipe has been closed, it generates a signal (of + class SIGPIPE), but if you tell the OS to ignore signals of class SIGPIPE, + then instead of generating that signal, the system call to write to the + pipe just fails. + + Pamexec writes to a pipe when it feeds an image to the user's program's + Standard Input. Should the user's program close its end of the pipe (such + as by exiting) before reading the whole image, that would, if we did + nothing to deal with it, cause Pamexec to receive a SIGPIPE signal, which + would make the OS terminate Pamexec. + + We don't want that, so we tell the OS to ignore SIGPIPE signals, so that + instead our attempt to write to the pipe just fails and we fail with a + meaningful error message. +*/ + struct CmdlineInfo { /* All the information the user supplied in the command line, in a form easy for the program to use. @@ -108,9 +130,25 @@ pipeOneImage(FILE * const infileP, tuplerow = pnm_allocpamrow(&inpam); - for (row = 0; row < inpam.height; ++row) { - pnm_readpamrow(&inpam, tuplerow); - pnm_writepamrow(&outpam, tuplerow); + { + jmp_buf jmpbuf; + int rc; + rc = setjmp(jmpbuf); + if (rc == 0) { + pm_setjmpbuf(&jmpbuf); + + for (row = 0; row < inpam.height; ++row) { + pnm_readpamrow(&inpam, tuplerow); + pnm_writepamrow(&outpam, tuplerow); + } + } else { + pm_setjmpbuf(NULL); + pm_error("Failed to read image and pipe it to program's " + "Standard Input. If previous messages indicate " + "a broken pipe error, that means the program closed " + "its Standard Error (possibly by exiting) before " + "it had read the entire image>"); + } } pnm_freepamrow(tuplerow); @@ -171,6 +209,11 @@ main(int argc, const char *argv[]) { parseCommandLine(argc, argv, &cmdline); + /* Make write to closed pipe fail rather than generate a signal. + See comments at top of program. + */ + signal(SIGPIPE, SIG_IGN); + ifP = pm_openr(cmdline.inputFileName); for (eof = false, imageSeq = 0; !eof; ++imageSeq) { |